<human>: I have an apartment. I decided to take a roommate by subletting the bedroom out. I asked for a deposit of two months worth of rent.

The subleaser's father gave me a check for that amount and also gave me a contract that they signed that basically outlined the terms of the agreement, meaning they get the deposit back so long as they stay for the agreed amount of time and there's no damage. As well as a few other very normal things none of which I had a problem with.

I never signed this agreement or deposited the check mostly because I'm not sure whether or not I can sublease the room in this state legally without the permission of my landlord. 

In any case, five months into the lease(if you can call it that), I believe he's abandoned the lease and moved out.

I've still got the check. And the bank it's with accepts and cashes check as long as they are under six months old. Which this is, just barely. 

Is there any reason I shouldn't deposit it? What is the likelihood of legal ramifications if any? What claim if any may he have to take any legal action against me if he/his father (the writer of the deposit check) feel that they are owed the money?

Am I the landlord in this case?

I was able to pick up the key from him and he noted that I have nothing in writing and that the sublease was not authorized. Now I do actually have a written lease agreement signed by him that I myself actually never signed. I'm not sure how useful that could be. 

Are there any due diligence I need to carry out to cover myself properly? Do I need to serve him any papers or file anything with a courthouse?

My prime concern is whether or not to deposit the check NOT whether or not  to keep the money once I do deposit it.

Give me the gist of the text in a nutshell
<bot>: Tenant/roommate abandoned premises. I have a shaky written agreement and a security deposit check that I never deposited. Do I deposit it and withhold until he pays his share of rent?