This may not help you with the affordability side, but many A/C units do not actually bring in air from outside, they expel heat/draw in cool using heat exchangers that don't bring in (or expel) actual air to/from the room. You may want to check the manual for your current A/C, there's an outside chance there is some setting to make it work this way.

Other than that, do you know why your landlord told you not to set below 70? Is it some technical limitation?

Anything below 70 and sometimes at 70 itself the unit starts leaking water. Here is a photo of my ac box I’ll have to see if I still have the manual around. How would the smoke not just drift through?

I found the manual right where I thought I might be but I didn’t see anything about air flow.

is there anyway to test it before I put it in the window to see how bad it would be, or is it just put it up and hope?

Make sure the unit is sealed in the window, and that the drain is not plugged up. It shouldn't leak water except through the external drain. A small filter that fits in a window AC isn't going to help.
Also, as a rule, AC units don't operate paticulary well at 70 and below.

i haven’t had a problem with the window unit leaking it’s the big centeral unit, which is why we bought a window unit, so we didn’t have to work the centeral one so hard.

I do have an air purifier for my room but I don’t think it’s good enough for the smoke.

I tried looking online for a filter that will work on smoke and for the window unit but I couldn’t find anything. Does anyone have any links to stuff that might work, be it filter for the window unit or an air purifier?

There's no filter for the window unit that would prevent smoke infiltration. An air purifier or HEPA filter unit in the room would catch only impurities/smoke already in the room, not prevent infiltration.

@solusumbra, I'm unclear, have you already tried the window unit and still notice the smoke? Or you just assume it will let the smoke in? The most likely place for smoke to get in with that unit is going to be around the edges and the accordion-style bits that are supposed to fill in the space in the window. It may require a bit of extra work and some imagination to do find a way to block air infiltration around the edges, but it shouldn't be impossible. Assuming it's a seasonal thing and you're renting, the plastic shrink-films used to help with air infiltration in windows (usually for cold weather) might do part of the trick, various airsealing tapes and whatnot in other places. You could try inside and out.

The other more simple suggestions if the rest of the house/that floor is at a comfortable temperature and it's just that bedroom: leave the door to bedroom open and experiment with a floor fan to get more air movement in and out (try different locations inside and outside the room and in different directions); use your drapes/curtains to keep sun out during day and keep the room from getting warm; or even a ceiling fan. You might find any/all of these preferable to a window unit, or perhaps reduce use of the window unit to only the absolute hottest weather.

I haven’t tried it yet since I assumed it would just flow right through and into the room.

Also we have tried the floor fans but it doesn’t work to keep the room cool.

Cigarette smoke can permeate walls to some degree. Because you're in a town home you are separated by a common wall. If your rental unit is in the middle you have two common walls one on both sides of you.

How can air permeate walls?

High pressure versus negative pressure. This pressure may be induced by what you are attempting to do to your room in addition to those on the other side of those common walls.

Air takes the path of least resistance and unfortunately is invisible. If a room is under negative pressure versus a room next to it that is under high pressure --- the air in the high pressure room will find ways into the negative pressure room.

Cracks and crevices.

Wall outlets, cracks at the floor where the base boards are. Etc.

Not allowing you to run the AC below a certain threshold is ridiculous. If you're paying the utility bill, the maintenance and repair of the unit should be addressed by the landlord. In this way I am using the term 'landlord' loosely, if you catch my drift.

The smoke isn’t coming through the walls but through the my bedroom window (when I have it opened) So I was worried about puttting the AC in the window thinking that the smoke would flow through it.

and yes I agree if we want it lower then 70 we should be able to, I feel like the centeral unit is to old or to small for the space but the landlord disagrees so I’m wrong.

By design, the outside air does not come into the room through the AC unit in the window. The inside air goes in, gets cooled, then comes back out. It does not mix with outside air.

The only exception I've ever seen to this are for units that have a venting function for people who want outside 'fresh' air to come into the room. It's usually a knob you twist that opens a small vent in the airflow path. If you don't have it, you don't have it.

When I had a window unit in my bedroom, I was prone to using duct tape around the edges to keep it sealed.

Internal seals (adhesive foam, rubber, styrofoam, etc.) on a window unit deteriorate over time which does cause more outside air infiltration. It's difficult to describe to someone who hasn't seen a window unit disassembled to understand the structure. A unit at my office more than 10 years old, mounted through the wall (no window, so no accordion side panels) on the south side which is subject to strong, humid wind on the Texas coast had deteriorated to the point that a bit of 'breeze' could be felt at times and the hot air infiltration in summer also threw the thermostat accuracy askew.

The situation is part-and-parcel of how window units are structured and can't be avoided as they age unless one has the gumption to disassemble it and replace or supplement the internal seals.

Thanks everyone for the informatio, so since my unit has the accordion sides what is the best way to seal them up or is there something I can replace

them with?

For how you can seal it up better: it really depends how much work you want to put into it and how handy you are - and also how permanent (assume you'll only want it for part of the year), how sensitive you are to how it looks, etc. My suggestion would be to install it with the accordion sliders and see how well it fits, and whether you notice the smoke, it might be okay as is. Then, do you want to be able to open the sides for normal air from time to time? If so, you may have fewer options. Are the accordion sliders removable?

Then you'll basically have to decide whether you want to do extra around the sliders (look mostly at the top and bottom), put something over it (how difficult to attach), or remove the sliders and fashion something to fit in their place (and how to attach that so it's fixed in place).

You could do anything from insulating tape/padding at the edges - which would be relatively easy to remove - to cutting something to size and attaching/sealing in place.

You might want to wander down to the local hardware store with some pictures and measurements and see what they suggest. If you're picky and don't mind spending a bit of money, perhaps you could find a handyman to rig something up.

Also don't know if security is an issue, obviously anything less solid is going to be easier for someone to get in.