We plan to buy a second house as well.

I know you don't want to deal with tenants and their problems, so why not either:A - Buy a NNN property where you don't have those problems, but still have cash flow,...orB - Take your $500k, and partner up with another investor where they deal with the tenants.

Quote from @Sundone Boutvyseth: Looking to buy a single family home and use as a STR on Airbnb.

I buy houses in the Memphis market.Terry Clothier REI Nation

Both of these allow you to low down payment loans to buy a primary residence with fixed interest rates.

You’re going to have to buy at least $1M (or whatever you clear after selling costs.), worth of replacement properties, not $500k.

You are correct, buying a four plex is tricky here putting 3.5% down.

We would buy this house all cash. 

We went from buying light rehabs to buying major foundation and mold issues to make numbers work until even that did not work anymore.

Airbnb is a company so the only way to buy one would be to own stock in the company.