Potentially you can buy a property with quit claim and deal with this problem later.

And these are very large contracts we're talking about here.At this point, I'm having some people tell me one day they could easily build 10 houses at once, then 4 days later it's like they lost interest in the whole thing.How itemized are these contracts usually?

And then 20 years later, when I go to sell them, will all the gains be tax free? 

My partner and I are viewing a property later and I’m wanting how do we find out how much to offer for the property.

repair requests, no rent, late rent, damages, etc, all are common, but a worn out land lord may be tired of them and want to sell.

These can be added when an initial offer is made or later  during the process.

That will happen later than sooner.

We are selling an old house in the Bay Area that needs a full replacement of a sewer lateral (about $7k).

and then later subtract this income from units that don't pay because of vacancy or credit loss by multiplying it?

In the other words, buying a rental today has a much better ratio than 15 years or 30 years later.