In that case, you'll want an attorney to make sure your right to have title transferred to you can be enforced based on the mortgage documents.In Illinois, when you buy a house with a mortgage, title to the property is transferred to the buyer at closing and the title is liened with a recorded mortgage. 

I will enforce it when I do a drive-by.  

You are at a less of risk for having your lender enforce some of these wild provisions...

Other than public records, there could be unpaid utilities, code enforcement citations, HOA Dues (if applicable) and open building permits that will stay with the property. 

Let the other fella deal with code enforcement the tenants and let him go over budget with the rehab on your asset

I would think you'd run into major legal issues if you even tried to enforce a lease clause or an eviction for too many guests.

Even if you have "be a good neighbor" items in your lease, they are really hard to enforce in court...... they wont hold up....You enforce the lease about no smoking....Noise.... call the police.

If the basic elements of a contract are there in the active document (offer, acceptance, consideration), with all the proper information (correctly named parties, legal description of the property, price, terms and dates), you should have an enforceable contract. 

On my application my applicant gives me approval to submit inquiries about them for both the approval and enforcement of our lease. 

It's not likely that a court will enforce specific performance against the seller.