New Investor; Tenant query.

[Tsering Lhamo]

Hi Fellow BP members,

I am a new investor and started renting for first time after purchase of my Duplex. I have a property manager. So one of the tenants saw property and we received one month security deposit to hold the unit (way back in mid Feb) and he was supposed to move on March 1st. He still hasn’t moved in because of some medical issues (as per him) and hospital admission  etc etc and saying will move March 15th now. My question is ,Does the lease start March 15th and I get only half months rent for March or I should get full months rent since that was the agreed upon date. Also if he just postpones again, Can I keep or reduce the deposit money for rental loss? 
My property manager is saying I have to return full deposit if I decide not to have this tenant (was supposed to move in March 1st, still haven’t moved in with first month rent ) or lease starts when he moves in. That does not seem right or fair. Not sure if that is true or she is just being indifferent to my business. And I have blocked or kept this unit because of security deposit since middle of Feb. Please advise, I want to start on the right foot.