Make sure fourplex is in decent shape or are able to make major repairs/have funds to do so. 

House was in bad shape with outdated carpeting, wallpaper etc....

Condo is in a great shape and would need minimal annual repairs with everything external covered by HOA.

If it either ages in a worse shape than it is now or I get ready to sell the building I will have to do something else.

I also always worked in construction in some shape or form (i grew up in it) and frankly I just love doing the physical labor.

Our place is 28 years old so it is in great shape so it requires less.

Maybe it's your unit that needs improvement and you can do that over time, while the other units are in better shape so you can lease them at top of market rates from the start. 

Some of the usual reasons why people would sell to these companies: If there is money owed on the house, the house is in terrible shape, you don't feel like dealing with selling it, or you don't want to pay realtor commissions.

The drive is a horseshoe shape around the back of the building (only one building on the property).

The driveway is 'Y' shaped, very narrow from the street to the back, then both houses have their own parking area in the back.The issue he is having is the other homeowner is 'accidentally' leaving nails, screws, and other puncture problem items on the driveway with alarming regularity.