Do one thing and do it well, there is too much involved for you to do both at the level you would need to gain and retain clients. 

At the moment I’m on track to buy 2-3 properties a year but it sounds like my income level is significantly less than yours.

I don't deal with renting RV's on the personal level, just working in the RV Park business where RV's can be rented within the park setting.  

I've also seen square footage of finished sunshine basements and even the lower levels of splits (where the lower level starts about two feed underground and all the windows are above ground level) not counted as square footage.

I'll actually need $275k to get the project done and the guy I had hired walked off the project during the beginning of COVID and basically isn't coming back because he's so busy with more lucrative business.At this point, I'm not sure if it's worth it to sell at a loss ($40k loss), or wait until lumber prices come back to 2018-2019 levels and just pay Property Tax on the land until then, or just spend the extra $100k to get the duplex built with a different builder and call it a day .... 

Given the level of rehab likely needed, even with the back taxes owed, why not try to list or wholesale this property?

My guess is that the two lollies were not leveled properly, and the weight of the 2nd floor shifted, causing increased pressure on other joists and a new set of problems over time. 

That industry isn’t projected to exceed 2020 levels until 2022.

The high level Lions that delegate or rely on 'professionals' because they aren't to be bothered with such petty things should work on another business.

Most agents don't break the 30k mark for at least a year in the business, so it could take a while to build up to your income level again.