But enforcement is based almost exclusively on whether a neighbor complains.

So it will really come down to enforcement or lack thereof. 

My original thought remains, sign the tenant to a strong Lease, enforce the terms of the lease, and see how it goes down the road. 

80% of our tenants have paid as of today and considering we cannot enforce late fees in our state until after the 10th of the month this is about normal. 

It basically gives the buyer the seller's rights to collect/enforce leases which buyer has to honor in any case.  

The downside for Bob is that the bank may learn of the transfer and decide to enforce their "due on sale" clause.

Many HOA's have no teeth to enforce what they are telling you to do.

As a real estate and litigation attorney I've fought, enforced, foreclosed, negotiated and defended 1st and 2nd mortgage liens - but never thought to invest in them [smacking head into wall].

They are all month to month, so you could just enforce the higher rent with 30 day notice. 

So,yes, it is for us to judge, there are minimum standards and they should be enforced