Is it okay to ask for 2x deposit + 2x rent (first and last month)

[Kareem Aaron]

Since all the applications I've been getting have really bad credit scores, and having gone through evicting a tenant who couldn't pay me three months' worth of rent, I decided to ask for double deposit and first and last month's rent.

The applicant I approved signed the lease with these fees specified but upon moving in, he only paid me 2 months' deposit and 1 month's rent (I was in a hurry when he handed the payment, I just assumed he paid what was agreed on in the lease).  

I found out later that he didn't pay the full amount and talked to him about it, he said it's illegal in the state of Maryland to ask for 2 months' rent on top of the double deposit, even if it's specified on the lease and he signed it.

I already talked to a lawyer about this, I was told that he isn't aware of any such laws in Maryland prohibiting or allowing landlords to ask for 2 months' rent in advance on top of a double deposit. 

Would anyone know if it is indeed illegal to ask for 2 months' rent besides a double deposit?