Some of it can be temporary, but ideally you'll want to be in markets where it can be sustained (ie. have barriers to entry). 

It's really up to the individual investor (and their coach who helps them create their criteria and decision-making process.)

I reached out to the individual marketing the deal to schedule a property viewing, but they’re asking for proof of funds (which I expected) and a signed purchase agreement or LOI.Is this normal?

Generally, I'd look for the ideal: % based mgmt fee with a cap on the value.

Mexicos second largest revenue source are wired funds from the U.S. by individuals.  

They can't assess all the subjective data like overall layout, view from the living room window, the dogs next door that bark all day, the width of doorways, size of individual rooms, quality of kitchen cabinets and appliances, etc.The best thing to do is study your market regularly.

I would prefer an individual PM (not associated with any company) to manage my 3 doors in FL..

Every individual contract is different.

Ideally looking to cash flow positive on all properties.  

These costs for most of the individuals are considered personal in nature (unless you have a RE portfolio that is run like a business; see below).