It could be a nice opportunity however I would be certain they will want you to make up the difference between $250,000 and whatever is left on the mortgage which btw in my opinion should be done with lender's knowledge and approval. 

Yeah, no pre-approval for us as well.

Any legal issues I should be aware of in this situation? 

Upon inspection the appraiser will see the crawl space and see it was a mobile home plus a HUD tag and public record.One of the requirements in mobile home financing is the property "Must" be on a concrete permanent foundation(in order to be real property) on top of that it requires concrete pillars, skirting and the "Well and Septic" dug and placed within legal distance from subject property.

I am too lazy to look it up, but pretty sure it is legal.

It's completely legal, very simple but powerful.

How keep it legal of course but more importantly how to do if effectively.

Additionally, we are approved with the Better Business Bureau (BBB).

You will want to consult with a lawyer.In regards to your last two questions here's some background on what makes a contract valid and enforceable:Offer: A promise to do or not do something within a certain time period Acceptance: A clear and direct statement that all terms and responsibilities are accepted Consideration: A legal and adequate inducement given in exchange for the promise Capacity: The parties to the contract must have the legal capacity and competency to contract Awareness: A party must be aware of the contract Legality: The contract must be legal in the jurisdiction it will be operating in***Not legal advice*** Steps I would take: -Review contract in detail to understand each counterparties responsibilities (if you are not aware)- Email a copy of the lease to each of the tenants listed on the lease and reiterate lease expectations for termination notice, rent payment etc. - If the lease was signed via Docusign (other esign may have same ability) - you can go to the envelope, go to history and view the IP addresses for each action taken.

., AirBnB) as it will expose your property to bad actors.Law enforcement and the legal system seem to operate quite slowly out there.