Talk to zoning about possible simple storage structure.  

The cost of repairs and tradesmen seems to have skyrocketed after covid, a simple pest control for ants costs above $250, whole house paint of a 1400 sq ft 3 bed house costs $4k or more, a new HVAC costs about $6k, a plumbing repair costs $200 or more, a new water heater costs $1000-$1500.

My extensive experience with heirs and probate tells me that nothing is as simple as just buying your BIL out.

I own a triplex and was wondering if I could use one unit as a short term rental to offset my W2 income as a trader business.

There are a few ways to go about structuring the financing on investor loans with flexible terms to up to 85% loan to value. 

We have short term rentals and have been notified several times upon guest arrival that the smoke alarm is beeping. 

As mortgage rates eventually drop, your cash flow should improve over the long term.

In terms of property management I have zero experience and wanted to get feedback on the hourly commitment so I can determine if I should self manage or get a pm.

It could also be worthless if they are only doing long term rentals since its all passive income...

It isn't a simple "yes/no" response.