I'm trying to analyze my first property and not sure how to set it up to run the number using the calculator tools here. 2 of the units are successful Airbnb short term rentals, and the other two units are month to month rentals to existing tenants.

The picture they have on Zillow vs one of the several I have with the same view:Your pic is better than the PM's pic, but that pic isn't why your unit hasn't rented. 

I used a hard money loan to purchase this off market deal.I rehabbed the upper two units within two and a half weeks and have a renter already lined up for one unit.

The only times this makes sense is if you are in a really hot market, especially seasonal ones where you might have 100% occupancy for the summer months or something.

That isn't written somewhere specifically that way, but your lender will ask why you would move your primary from (for example) a 2,000 SF SFR to a 750 SF unit in a four plex? 

For rentals, would a single floor or two floors makes sense? 

Lets start with when it does not make sense: Owner finance does not make sense when the borrower cannot afford the property. 

If you're younger then it might make a ton of sense to take down anything you can as long as it cash flows. 

The idea is to convert a multi-family building into condos; but not in the traditional sense where you separate pre-existing apartments into their own condos; but in a way where you combine the common areas of all of the apartments in that whole building, and turn the individual rooms within those apartments into condos themselves; thus transforming the hallways, kitchens, bathrooms, living rooms, dining rooms, porches, balconies into common areas of the condos. 

Let’s look at the math.Pre-Covid, the National Apartment Association (NAA) released data showing that the average renewal costs between $5,000-$10,000 per unit.