The next day, the neighbors were upset that I am blocking their window.

You may be a volunteer/humanitarian, but that does not include your REI business. so point them towards some help and hold them to their lease agreement.All of my good faith would have gone out the window once they lied to me about stealing my check. 

Maybe plan on showings only on certain day/time windows to accommodate their schedule.

That house was renovated (by seller, not me) and passed inspection (minor issues repaired) but until a house is stressed by daily living with  the occupant turning of faucets, heat/AC, opening windows, etc., a renovated older home will still have issues.

There can be assessments for windows, roofs, siding etc that will kill cash flow, the HOA fees generally make the numbers not work and if the fee is too low, it's likely in an area you don't want to own in.

DC will require you to have 2 egresses, so you will need another door, or larger windows (with no bars). 

For illustration purposes, the windows are a 4 week lead time so you put the window order on your card and once they are installed, your lender releases the funds and you pay down the cards.I see too many “Gurus” teaching new investors how to use credit cards to cover down payments and they teach this because it creates the false perception that anyone can buy real estate with or without savings.

Since I don't know what I don't know wondering if I am spinning my wheels considering approaching the condo board before purchase to find out if they would allow window replacement and if so point me in the direction to get some quick quotes so I could put together an offer. 

Also, there is no visible mold and no mold smell in the basement (there is a little on the caulking beneath a single pane picture window upstairs which I'll deal with).That didn't sit too well with the tenants as they have been looking online and finding information about how dangerous it might be, and it didn't help that the first report that I had done the inspector attached a boilerplate message recommending a full HVAC cleaning (ducting is 1 year old) HEPA vacuum, air scrubbers, double washing everything in the unit with bleach, etc. so now the tenants are being fairly combative and insisting that more needs to be done.

The tips I got from the inspector was to make sure you wipe down the window sils and similar things in the home.