As with most municipalities and jurisdictions, the evolution of the AirBnB market has spawned regulation and restrictions on where, when and how a STR can operate.

It's important to stay informed about developments in the areas you're considering, as well as any potential changes in regulations or economic conditions.

build to rent is great. they are an intermediary that help investors contract direct with turn key new build. they are pretty sophisticated we have sold a house so far and we are looking to sell other multifamily with them. there is a vetting process and as an intermediary they don't control construction they help vet builders and establish relationships. they have a big team. the other builder I've never heard of but unless you can see your house I wouldn't touch it. rent to retirement has a strict policy of 90 days until certificate of occupancy until they will send a deal out they are good at what they do and I'd recommend them. they have options all over the country and established relationships.

Airbnb properties can be hit or miss depending on location, seasonality, and regulations.

I also doubt very seriously that any brokerage/custodian is going to allow this kind of loan with 401k assets; it's likely going to need to be a 401k general purpose loan, which is highly regulated (as someone else mentioned). 

Then there’s city regulations—some places heavily restrict short-term rentals, so you’ve got to check the rules.If you find the right spot and automate stuff (guest communication, cleaning, etc.), it can be profitable.

Between the main semi-monthly meetings and the various sub-groups there are probably 5-10 or so potential meetings each month that are strictly content and networking with local investors.  

Proper underwriting - this includes an appraisal, loan app and full underwriting to comply with CFPB regulations.2.

I've been corresponding with a non profit in CA that is doing work on ADU regulations, etc.

If you're going to do it alone, make sure you your due diligence: estoppels, inspection, review, consult with a local attorney familiar with the local regulations, etc. and good luck.