**I'd settle for recommendations for reliable brands with good performance for a natural gas condensing combo tankless water heater and air handler setup. Any more info for additional questions below is optional. Have a deadline mandate from condo association for replacing hot water tanks over 8 years old which is why I am dumping a lot of info and questions.

[Optional additional questions / info if people have time]

Not as easy to research as other topics. Not making the progress I should so turning to people who know way more than I do. Intended to be a couple quick questions but snowballed.

Looking to replace hot water tank and upgrade my HVAC central air handler with high efficiency condensing combo unit.

Will keep the A/C part of the HVAC system for now.

People may want to say I should consult a professional. That's because they probably don't live in my area where even a company with an "F" BBB rating has no shortage of work. Have also come to learn that having a top level certification for a brand in no way indicates level of competence. Or the brand backing their certification. Literally just one headache after another no matter the industry or vendor. So, I need to know enough to not end up with a BS result or installation. One manufacturer, I looked at the reviews of their top tier contractors in the area. All had terrible reviews. And not likely all competitor spam as reviews were calling out workers by name. Plus I have unique issues which contractors tend to ignore since outside their knowledge base.

1) Any brands that are generally considered best for performance and reliability with natural gas fuel source?

2) Is it better to hire through a website like houzz or angies list than to contract direct? Noticed the contractors with terrible ratings from yelp and other sites, had good ratings on angies list. Do contractors tend to do a better job from a referral service so they don't get tossed off or something? Didn't see a way to search for specific contractors on houzz.

2) Currently have a run of the mill 80% efficient single stage air handler rated for 88,000 input BTUs which means output should be about 70,000. Rinnai website shows their combo boiler and air handler units max out at 60,000 BTU heating capacity. Does that just rule them out?

4) Is reusing my existing central air A/C evaporator an issue? Want to replace in the future after renovation makes my place more energy efficient. But not now. I'm fine with custom duct work if needed. I wouldn't miss the Jenga looking thing I have now.

5) Do you have to worry about pipe failures and flooding with these types of set ups? I live in a condo and my downstairs neighbor would be most affected by a water leak. As well as me for paying for the repairs, again. A tank water heater I have an overflow pan under it. Is there maybe a leak detection feature that can tell the difference between a leak an a hot water demand?

6) How is maintenance compared to a run of the mill gas fired HVAC handler? I have city water with plenty of minerals. But not "hard" water. If that is a factor.

7) A duct mounted evaporative humidifier that routs humidified air back to fan before the heat exchanger shouldn't be an issue?

General Features (not looking for an exact model match. Just adding in case off the top of ones head it makes a difference for brands or I need to educate myself on something in particular):

-Variable stage fan would be nice. But definitely don't want something smart enough to factor in return air temp since that has air from outside the home too. (will fix someday)

-Separate hot water and water for heating for different temperatures.

-Don't want the pump option to circulate my home for immediate hot water. I can wait. Assume air handler or combo boiler will have some kind of a pump for heating.

-Combined combustion air / exhaust pipe 35 to 40 vertical feet. (likely an option for any unit, handled by piping?)

-Condensate neutralizer to keep pipes safe. (likely addable for any unit's condensate drain piping?)

-Prefered but not a deal breaker, leak detection with shutoff

-Any other features recommended?

Hard to tell my CFM needs. Supply leaks like a civ. Return side isn't even fully connected. No way to know how much air is from inside condo, and how much is succed out of my neighbors place, from the attic that the chase leads to, floating around between floors since fire rated chase is wide open in some spots, and haven't yet sealed the gaps around the framework that allow air behind walls, between floors, under floor on first floor.

Heat load calc shows my furnace is over twice what it should be...If my place was actually sealed and insulated with proper ductwork. Would like to continue to seal and insulate my place as well as replace most, hopefully all existing duct nightmares. Which would change heating capacity needed down the road.

Would be nice if these combo units were adjustable to accommodate half the capacity in the future, give or take? I did see on the Rheem site their combo boilers have a large min/max range. 16.5K to 99k for example. Don't know if it is common to be able to adjust heating level or just these units. Didn't see anything like that for Rinnai.