We had flat roofs and our stipulations were installers had to arrange appointments with our maintenance tech for access to the roof. the dishes were required to be on a Sleigh. 

This is such a state-specific and contract-specific situation.Here in Texas, if there's financing involved, the buyer can cancel the contract and receive the EM deposit back if they can't lock up their financing with X days, which is stipulated in the contract.

My question is: Is it legal for me to rent the main house to one family and the in-law unit to a single person (with stipulations on no or low visitors, noise etc).

I would give her permission to install her own key lock on her bedroom door with the stipulation that you receive a copy of the key for access within 48 hours and she returns it to normal before leaving.   

The FCRA stipulates they must VERIFY with the creditor.

@John BaskinHello my name L'Oreal and I do remember reading about FHA investments in the and did to be careful with FHA bc they stipulations such as the 90 day own rule.

@Andrew Robitaille you know your situation and I stipulated that it might not apply to you.I'm not getting your business but want to clarify, you said "debts".

Yes it is the basis to settle a dispute, but if that contract stipulates that in the worst case scenario, I lose an immaterial earnest deposit for breach, then I really don't feel too obligated in a legal sense.

Quitclaim buyers onto title with side contracts stipulating they get off if can't refinance house (which can often be easier) into their name in certain time frame?

They may stipulate that if pulling money out to purchase, it must me a primary residence or even your first time purchasing.