A third use is lead acid for batteries.

I already asked if they would approve increasing the amount but because it's now purely an investment property, they cannot increase the limit.

Any suggestions for an inexpensive preferably battery operated intercom/doorbell?  

@Matthew PaulThe worst part is that is actually the best advice from a purely financial standpoint.

The only thing to consider is the batteries need to be changed every three months and it requires internet access to operate.

I am doing it, right now, purely for the practice, reps and insight.  

But for my retirement, I'm focusing on pure cash flow deals.

Those batteries are not cheap and have short life-spans.

Build it for pure STR.

Some might argue for appreciation but that would be purely speculative.I see it could have been a popular idea in a pandemic-stricken world of 2020, but I'd place bigger bets on traditional residential real estate.