All bedrooms are on the 2nd level and there is a big open loft area with windows on 2nd level that's not used much now.

The property features two 1,400 sq ft suites on the main level (one currently leased) and over 3,000 sq ft on the upper level, with 750 sq ft already occupied, 3 small office spaces (+/- 250 sq ft each), and a basement tenant with 1,400 sq ft of storage space.The building generates $6,000 in monthly gross income from its five tenants, but with full occupancy and market-rate rents, it has the potential to bring in $10,000+ per month.Given its historical significance, stunning architectural details, and location, I’m curious about your opinion: Would this property be more marketable for sale with or without the current tenants?

I'm in a similar situation where my split level basement has it's own exterior entrance and and glass sliding door. 1bed1b, kithen and laundry room. 

All short-term rentals have some level of weather risks, I would say.

It’s a bit of a fixer upper, but in a great location. 

There has been a considerable amount of foundation work done (addition for piers, leveling, etc).

At a technical level you have two paths, either 1) combining the bottom and ground floor units into a larger unit as you suggested above or 2) create a third legal unit.

Happy to share if you're interested.Accounting systems are great: QB, Stessa, Digb but the reality is you want to track a few things at a high level, this will make your life a lot easier when you sell/need to report income/loss, and accounting systems won't always make this easy. 

Look for cracks in the foundation, walls, or ceilings, as these may suggest settling or shifting.Additionally, keep an eye out for pest infestations, particularly termites or carpenter ants, which can cause significant damage to wooden structures.Lastly, be aware of environmental concerns such as radon levels and underground oil tanks, which can pose health risks.Having a qualified home inspector conduct a thorough evaluation is essential.

It is no different at a high level.