In fact, the typical AC is 12,000 BTUs or one ton larger than it should be for the space in which it is installed.

Concrete is porous and will otherwise absorb liquids and possibly stain. 

I'm hoping you can help me figure out how to qualify for a larger conventional mortgage, right now I can only qualify for about $450K with 5% down, which is my goal. 

If you want to work for an institutional investor or have any desire to play in the middle market or above [which the best way to do the latter is to have worked at for an institutional shop] then a degree is a requirement and if you want to work at the shops that do the most interesting deals [family offices, pension funds, REITS ect] you will have had to work at some of the larger firms to cut your teeth and they do care where you went to school.

I started to find a few solar companies installing solar on larger multifamily then billing each tenant for electric directly.

For larger jobs like this it's always best to get several quotes so you know what the market rate for the job is. 

If my business was new at the time and wouldn't be carrying larger balances, it is simply annoying to pay a bank for not having 1500/2500 minimum average balance.

Every few years the assessor may do a drive by of a property, but it's likely not a frequent occurrence, especially in larger counties/cities.

I work with a bunch of hard money lenders that fund units that size and larger.

So unless you have $1M liquid net worth or >250K income you are precluded from a lot of that.