Work with an agent you can trust. You'll probably have to pay a fee but at least you'll get an apartment and know where the money went.
So taking Rent.com out of the equation, it is not common for a landlor to request a deposit to be held in trust to view a property. They will say it's held in trust and perhaps use Rent.com, but I'm sure there is no such agreement in place and it's only a scam to get gullible people to believe it true. Use your head!! Think. If it doesn't sound correct, do not part with your money.