Duplexes are cheaper to rent and expenses are becoming difficult for the average tenant.  

What you want is an agent with experience who knows how to negotiate, watch your back, navigate difficult situations, understand contracts and law, provides an objective cross-check, etc.

It's difficult to see how a tenant will be after screened and signing a lease.

Were waiting to see how things are by the end of July here in CA (heros act ect) to see if we can serve her then, but even so, I imagine it will be difficult but I will mention this time him and see if theres hope lol.

Add the difficult exit and your investor pool is very limited. 

As mentioned 90 day limit, which makes it difficult, and wuite pricy to get the STR certificate from the city. 

I do not know him, but the path he is leading you is a difficult path    Note difficult does not imply impossible; there are people who are successful with S8 housing    In my area s8 is so undesirable that they write laws trying to make it challenging to not allow S8 tenants.  

. - cash flow is difficult now with long term rentals even if you pick markets that have lower purchase prices than Boston.

It almost feels like they make it difficult on purpose so they get extra revenue on late fees.

It is rather difficult to make BRRRRs pencil out right now, so you should budget to leave some capital in the deal on the refinance.