WHERE VACATIONS START!
Your last question is a good one. There are some limited regulatory agencies that can help you if your landlord defrauds you, but it will wear you out trying to get their action. Or you could see an attorney to help you, but it would likely cost you more than you were going to recover. So, your due diligence needs to include an assessment of the integrity of the landlord and their reputation in the community.
My response to your first question is based on my own prior experience in renting and selling properties. Most people want to tie up your ability to rent or sell by placing a small deposit that they are willing to lose. But, the property owner loses far more in both money and time if the renter or buyer defaults. The deposit is a gage of their sincerity.
The prevailing wisdom here is not to rent or buy any property sight unseen. One of the most important considerations is that if you advance money, both the money and the property may be gone when you arrive. I've heard numerous instances of this happening. And, as Bill says, recovery is largely impractical. I hope you're one of the lucky ones who gets through this unscathed financially.
how do you know who to trust?
Ask for references.
They're clean and wear white socks.
My advise to you. Use an experience and honest Realtor, make sure you have a contract in place before putting any money down, review it and make sure is notarized. Best of luck.