Of course there are no guarantees, with this, but what are some ways to prevent people from dumping on your neighborhood

Depending on the location of the property, there are different laws that prevent you from overcharging (flat fee).

When I called a few days ago to ask whether there were any issues preventing him from executing the deed / closing docs at the closest US Consulate (as we'd discussed previously), he denied having ever received the closing docs, and much worse, now denies having ever signed and returned the sale agreement to me in the first place, and is asking for a large price increase. 

Buyer's Agent: Michelle Lorenzetti of Investors Connection CT Insurance Agent: Justin Sloan of BSP InsuranceLender: Gary Root of First Choice Mortgage Services, LLCAttorney: Joette Trinh of Keily Mira Law

What's currently holding me back that I'd like to remove are the barriers I have that prevent me from getting a mortgage quickly.

Today's Financial Times (subscription needed to read the full text, this is just the headline):US financial regulationFed officials call for tougher rules to prevent asset bubbles Officials worry that low interest-rate policies could encourage excessive risk-taking

What’s to prevent me from asking for less of a down payment?

I can't prevent that from happening but did let all the students know that the full rent must be paid.  

In fact, many economists have openly urged the federal government to pass another major financial relief bill to prevent the recent economic progress from stalling.

There are other rules though that you might want to prevent a weekend from getting blocked off because of a weekday stay bleeding in.