[davchana]

No 3 letter.com domain is available to register (all combinations are registered, can only be bought). 4 letter mixed numbers letters are sure available. I am not sure of 4 letters only is available. 5 letters only sure is available.

[bombcar]

I bought a three letter domain at one of the original TLDs for $3k or so, they can be surprisingly reasonable depending on your use case.