It's a common tactic used by get-rich-quick gurus.Some options do exist but they are difficult and rare.

It is a process which will probably involve giving them notice and a chance to correct, before you can ultimately do an eviction.Either way it sounds like they are/will be difficult so I would strongly recommend consulting an attorney who specializes in evictions.

The reason is that the price range you outlined is likely to put you in C or worse areas and those can be very difficult to manage effectively. 

A tear down and rebuild is difficult enough for a seasoned investor let alone someone new to it.My wife is in medical school so I can relate to the concerns.

If I wanted to update the principal balance and terms of the note, is that something I could just add to the existing documents as an amendment?

Not that difficult

They are extremely lucrative and if you already live in Scottsdale, it would not be difficult to manage yourself and save some fees. 

It shouldnt be difficult for you to reach out and work with wholesalers in the areas you are marketing for deals.

I would like to know if I could us my solo 401k to cover the deposit, and obtain a mortgage from a bank for the balance.

We all know connecting with some agents/brokers are difficult.