You definitely don't have room for a (parking functional)circular drive at the front, and in any case this wouldn't fit 4 cars. If the alley is also driveable, your best best with least amount of additional paving to be added would be to also enter at the back with vehicles, and maybe add a garage/storage shed at the back property line. Otherwise, you don't have enough room to park cars side by side at the one side driveway either, and if you don't want to pave over the front, you will need to have cars drive all the way into the back for all of them to park off-street, and yet not block each other getting in and out. I don't see how you can realistically accomodate even 4 cars off-street without paving over most of the back yard. If parking in the back for 4 cars is the desired solution,you might also consider using a product like turf block instead of solid paving, as this can be turfed, still looks green, yet also allows vehicles to pass over it. This may not be as commonly used back east, but is a good solution in California gardens where you need off-street parking, but still want it to look like softscape rather than hardscape. As to your question about the back stairs, the long run of stairs across the back could be switched out with a staircase that extends out into the garden and then doubles back on itself, to avoid closing off the middle window. It would also be more expensive to rebuild the deck to enlarge it and reorient the stairs, but if you have the budget, it could make for a nice useable space at the top level, and a more aesthetic stairway down to the garden. You'd probably benefit from having a good site planner/landscape designer/landscape architect familiar with what is permitted in your area, to help you think through various alternatives to your dilemma. I've handled similar situations here in California where a duplex was being turned into condos, and the backyard garden design needed to allow access all the way into the back for potential parking. In my case, the actual garages were at the back lower level of the units, but had been turned into living space/offices/storage, and not really intended to be used for vehicles. We also had a similar even more narrow driveway at both sides of the units. The reality ended up being, we added a gravel driveway and flagstone patio that could allow for access to the garages, but only 2 cars parked on site at street driveways,(forward of the house), and the others parked on the street. The long driveways became additional garden space, while also keeping the paving to allow car access if necessary. Your other question about unclear entries is probably best resolved with a permanent decorative address sign with arrows at the juncture point of the combined walk, or at the corner of the house. The one walkway from the street and the second unit's doorway that doesn't directly face the street would make it confusing for first time visitors. Alternatively, why not add bolder street numbers near each door, and make sure they are also lighted up at night. Oh, congrats on the new house purchase, and I hope you enjoy playing with the new house and garden layout...

Again I disagree....and the part where I think you go awry here is in assuming that this shade, which I describe as sufficient to park a car under-just got there today. This tree is of course still growing, and this rather wet summer we're experiencing so far is surely boosting that growth. But if it is-for purposes of this discussion-exactly 50 ft. tall now, do you think it was what...15 ft. tall last year? Of course that's not the case. It was nearly as large last year as it is this year....and it was nearly as large two years ago as it was last year. Again, I'm not at all sure where your general idea of tree growth rates come from Embo, but they seem decidedly out of step with things I see every day, here in one of the shortest growing-season regions of the country. Maybe pergolas and trellises would be a great option for OP here, but that was not and is not the question being asked. I do try to answer that which was asked, not send things running down a new channel. Nor do I insult the various posters' intelligence by immediately assuming they have no sense of time. I'd be willing to bet that Daniel here knows it takes time for trees to achieve their "mature" size.

The picture looks to me like the street is gravel and there is no particular part of it that belongs to you. Where is the actual property line ... somewhere within the grassed area? If that's the case, you have no legal right to restrict parking. I understand how people like it when the street parking in front of their house is left for them, but there is no way to command or guaranty it. As a rule, people TEND to park in front of their own house on account of convenience. But when you tempt them with nearby shade, it's going to be an incentive for them to work against your wishes. You could be cute about it an install a sign that says "Parking For Irish Only" ... or Cherokee or whatever works in your situations. Or just talk to them. But caution, neighbor's can become very touchy and might rebel on account of your not actually owning the parking space. Is there a possibility that you can park some vehicle there frequently enough that you can subtly send the message you want to actually use that parking space? They might relinquish or at least use it less. Landscaping -- planting -- a portion of your yard, such as an island around the tree that comes right up to the curb, might tend to indicate that you'd like more control of the space. If you can't find something that's subtle or a friendly way of gaining control of the space, I think you could risk starting a battle. Sometimes those evolve into wars.

In general the extra living space adds more value. But only you can decide if losing living space is worth it to you. You can be sure not to leave valuables in your car overnight, including registration papers and insurance papers.