The second home loan guidelines directly state "The Borrower must keep the property available primarily (i.e., more than half of the calendar year) for the Borrower’s personal use and enjoyment"This means that you can only book it out on STR platforms for half of the year (50% max occupancy), which really sets a cap on your max income. 

It will vary based on the lender's guidelines. 

And/or are you willing to take the risk of being sued by the seller for not performing on a legal contract (and losing your earnest money)?

Be sure to review the legal documents, oral representations won't stand up in court.

A real builder is supposed to do their own diligence and be savvy enough to know that access (legal access, not just does it abut a street) should be the number one thing they check first.

While many of these issues are important considerations and should not be ignored or overlooked, there are other more crucial criteria that you must question and evaluate first.The critical risk criteria that you must review and evaluate prior to making your final decision on which 1031 Exchange Qualified Intermediary to retain includes, but is not limited to, the following areas:Technical capability of the 1031 Exchange Qualified IntermediaryInternal processes and audit controls to safeguard your 1031 Exchange funds and assetsUse of Qualified Trust Accounts or Qualified Escrow AccountsDecision criteria and guidelines for investment of your 1031 Exchange fundsProtection from potential errors or omissions by the Qualified Intermediary (E&O Insurance) Protection from potential theft or embezzlement of 1031 Exchange funds (Fidelity Bond) An experienced and professional 1031 Exchange Qualified Intermediary will understand these concerns and should be happy to discuss these crucial issues with you.

If the seller misrepresented tenant conditions, consult a real estate attorney about potential legal action.

They all tell me to got to Legal News because all mortgage related things are posted by them.

(There’s no way to transfer title that can legally prohibit enforcement of due on sale, except transfer to the owners REVOCABLE trust or transfer to children upon death).  

If you need financial help, ask under the "Finance, Tax, and Legal" forum.