In addition to STR'ing the main house, he is building 2 more units (ADUs) on the back side of the property.

My idea is to get an apartment and make sure it’s okay with the owner to rent it out as an Airbnb.

I know a lender that can help with both states that does investment lending for very cheap, it would be worth a connection as you look to build out your team no matter what you decide.

Mine is a 2022 build  Hey Ryan, Your property checks alot of boxes for me for a MTR focused on attracting families as a whole home rental.Single story, Good school district, Little to no competition on Airbnb, No HOA.I bought a property once in 2015 and it barely cash flowed as a LTR but now 10 years later, I cash flow as a LTR about $600 per month. 

Cash flow approximately 350 a month.Option 2: Use the cash to buy land to build a 6 bed 4 bath duplex, all in cost approximately 300k/330k. 

It makes sense for your new build but you'll have leverage something (fixed rate) to get out of that loan. 

Are the new builds for owner/occupants or build to rent?

Bonus Tip: If this quadruplex is out of state, I’d highly recommend building a reliable local team (cleaners, handymen, etc.) and maybe consider hiring a co-host or VA to help with day-to-day tasks, especially if you scale up. 

(Insert some sincere rapport-building compliments or questions here - about their yard or dog or whatever.)  

We are currently building many investment Single Family Homes on independent lots that focus on maximizing rent.