You give them notice to cure or quit.

He is the source and the cure.

Maybe an 8’ vinyl fence but that wouldn’t cure the whole problem.

the main issue with this is if you don't personally have the funds to buy or cure the default .. and your buyers which you really have no control over don't come through .. the seller gets damaged big time. 

to complicate things, there is the foreclosure itself (trustee sale) which is held auction style at the court steps etc and then once (and if the bank takes it back) there is REO auctions (like auction.com) which liquidate REO after foreclosure.depending on each state rules, the foreclosure can be halted at some point if the owner cures the default (brings the loan current). 

WSJ post article titled: "Housing Market is Faltering and Strong Economy Offers No Cure". 

And st worst, they find out and give you X days to cure. 

In my experience with buyers, the best cure for “analysis paralysis” is to go see these “maybe” buildings in person - I promise it isn‘t a waste of time, it‘s an important part of learning.

And in a worse case situation the property can be deeded back to the seller curing the infraction.

As for the violation send a 3 notice to cure and hopefully that gets their attention.