I’d like to take the next step and become an on-site residential property manager.

The 'Silicon Valley' tag is the Forbes author's twist, but I think is clearly a bit of hyperbole designed to grab reader attention, something more and more difficult to do, especially for a piece of this length.

Are there sites other than AirBnB and VRBO that you would recommend that have a more extensive screening process? 

Solo 401k designed for those who are self-employed or own a small business with earned income and no full time employees (investment income won't qualify).

A developer typically will not buy a piece of land without getting site plan approvals, zoning, LOI's from tenants,etc.

I want to start prospecting probate leads, I’ve been on the website but what document can I find the subject property in?

Most counties will have information about their tax sales on their website. 

Driving for dollars or purchasing lists and your target audience. websites and such will come later.3) decide on what type of direct mail.

You can find them via BP and meetup sites.

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