In most states, the security deposit - if the amount is stipulated as such in the lease - has to be held in escrow for the renter and returned at the end of a fully executed lease minus any legally deductible expenses.

@Sam Sharata that stipulation on the use of the SD is weird.

if I purchase a fully occupied 4 plex with an fha loan that stipulates I live in one of units, how do you move one person out without raising  rents?

Typical FHA stipulations require you to live in the property for 12 months. 

If there are stipulations that would prevent you from purchasing a SFH then I would refinance the two family as you purchase the SFH. 

If vacant, was that a stipulation of the deal?

Yes, I would also have my contract stipulate that the items need to be removed.

He pays me $1/year rent on the shed.That's probably a little casual for your situation; I'd definitely set up a contract stipulating what, where, when, how much, who, etc. including who puts a lock on the door & who has keys.

@Jacob Barnhart you can stipulate in your offer that 1 of the units must be move-in ready by the close of the contract, then have closing after the lease.

The only exception to this I see is if closing is setup prior to the closing date stipulated in the contract itself, then I don't see any reason it can't be moved.Take an hour and read the contract and everything it says.