Due to recent security frauds and banks not covering losses adequately, apps like Zelle may not currently be the best option.

Like you, I was eager to start investing in real estate but decided to hold off until I had more visa security.

At the same time, I would reach out to that STR owner to try to get him to fix the nuisance issue.That said, even if you are successful in staving off the issue for now, it could come back at any time based on the current board members or on wide community support for getting rid of STRs.You could try to gather support for changing the covenants in your favor, but my gut is that that will be hard to do. 

Do you have to keep the security deposit in a separate account?

In addition there are areas in Los Angeles that have stricter rent control than the state wide rent control.  

First, request the current rent roll, which details each unit’s rental income, lease terms, and any security deposits.

I look at the tenant's financial situation (income security) as a very important part of the property analysis. 

. :)As a company, BP has wide reach now which brings a lot of spam and right now they can't keep up.

I used furnished finder and keycheck to find tenants, screen them, and collect rent/security deposits. 

An estoppel certificate is a form you have the tenant sign that confirms their lease start date, the amount of their security deposit, and other things.