I have a utility room that mirrors another unit in size, but it has heating oil, boiler and circuit breakers in it currently(all old, barrel plug circuit breakers and nearly 50 year old radiant boiler heat system for ...

Opening and shutting it hard may cause some damage or forcing it open.

Don't try to force cash flow by cheating the numbers.

Your buyer will be forced to cash you out OR you must have enough cash to pay off the underlying loan. 

No one wants to put 70% down, so that forces the buyer to get a supplemental loan at current market rates, “plus some” because it is a second lien.  

While you may not be able to force her out, you may be able to ask her to volutarily leave.

Some people I know have been as high as 400% increase in gross income in 2021 vs 2019.Everyone is aware of the higher supply of customers with more people forced to travel domestically and by car, but I think a big overlooked factor is the higher average wealth of those new customers which is driving up ADR a lot.The new supply of travelers in a lot of these markets are the people that used to take big expensive international vacations but haven't been able to do that the last 18 months. 

It is no secret and well documented that wealth is generated much faster from appreciation, both forced and market.

Tell them you won't accept it and they need to vacate or they will be forced out.

You could also consider a STR near Lackland Air Force Base, which hosts Air Force Basic Training graduations every Friday.