You can do some back of the napkin calculations to determine what the costs would be and what the potential revenues would be. 

Most likely you can write "I agree to pay $260,000 for the property at 123 Ontario Lane" on a cocktail napkin and send it to a title company and your bank.They will guide you through the rest.

(I'd like to put an A-frame on it, see: https://www.madihome.com/, there's a sanitary main but no water or driveway)- The closest water main is ~60m away- The closest street is ~60m away.

Could be on the back of a napkin if you're really in a bind."

all these rules are for napkin math.. also learn about IRR this is the long term metric that is most important.A lot of BP never talks about exit and long term value and the appreciation needed to make your IRR acceptable.

In my opinion, the economy of scale isn't there, or at the very least, is very challenging.That thought aside, a back of napkin figure suggests the same NOI using 60% of gross rent, but that back of napkin calculation is BEFORE debt service generally speaking, so you may be looking at creative marketing by the seller. 

As a back of the napkin I would assume a 50% expense ratio not including your mortgage.

Back-of-the-napkin math, but if your annual property taxes are half of that, then you will be coming out at about $200/month.

At least they are sanitary, I thought.

from pics it looks like mostly flooring and paint (to cover up these beautiful drawings)It was a back of the napkin estimate.