I've typed my response and tucked it away in my proverbial drawer. 

@Nicholas L. ideally I'd like to live in the unit but if I have to purchase something out of state then no

Last time I did that, my costs came in right at $1000.The OP is vague because it does not address size or location of heater, type of fuel, self-install or hired, permits required or not, and whether or not they care about a specific brand.  

What made you interested in investing in this type of deal?

@Kevin SiWe avoid window A/C units since this type of apartment unit only allows you to push the rents so high.

For 30Y loans made to an LLC - 15%-25% down minimum depending on what type of lender you are using. 

I would be using a DSCR loan since I don’t have 2 years of work history.You are mixing up loan types and I recommend to better understand these types.

My clarified question would be "if someone were in an ideal situation where they had a apt with good cash flow, what kind of factors would make them want to sell?"

All are 4/4.5/2 What made you interested in investing in this type of deal?

Not sure how long you have been around, but when markets soften, these types of assets get crushed because vacancy rates increase which causes condo fees to increase due to the amount of delinquency on the books.