For collections in Southern California, try Sutton Law Center or California Judgment Enforcement.

In particular:(1) Should I hire a law firm or collection agency to facilitate the transaction?

Non-US citizens can have LLCs in the US which will allow you to have a business in the US, pay taxes, and comply with laws.

Will depend on several factors like the type of property, type of tenants, your risk tolerance, other assets you own, your estate planning, laws where the property is located, etc.

I'm being told that the area will have zoning laws within the next 5 years so I guess it would be who of me to get this thing going.

@David Randolph - my use of the word "threatened" is in regards to the statements made by, as at the time I understood it to be, the real estate agent negotiating the sale to inform me that I could be sued and a lien placed because I was refusing to sell, which would mean that either I agree to sell and put my children on the street or I refuse and they will sue to take possession and I would still put my children on the street, I took that as a threat to the well being and safety of my children, legally it may not be a threat, ethically and morally, it is to me.

Depending on which market you plan to invest, it's also helpful to educate yourself on state restrictions + laws, rental property management etc. before diving in.

I've been house hacking my place (I rent out a 3-bed 2-bath residence and live in a small in-law unit in the back) for just about 3 years and have been setting aside money each month for my reserve fund.

If you're near a medical and/or law school, monthly rentals are preferred by those who are preparing for board exams over vacation rentals as well as by visiting professors. 

(Couldn’t really afford the place, didn’t have good enough credit to be worried about an eviction, etc etc..)2) They should have posted a 5-7-10 (depending on local laws) to “pay or quit” as soon as the ent was late and started eviction.