I have a separate interest bearing account for security deposits as required by my state laws.

I would keep the deposit unless I am able to rebook the dates and then I would only make her pay the difference for any unbooked nights. 

Yes, you can deduct the 8 days rent from the security deposit.

I also require additional security deposit and sometimes a guarantor if they were approved in this manner.I also agree that this situation sounds like a pattern not a one-time mistake or short term tough situation that caused this.  

We did give 50k deposit up front which he says he will use towards finishing up.

Consider all the things that could go wrong and see if the lease addresses them: unauthorized pets or tenants, early termination, security deposit, lease violations, late rent, eviction, lawn maintenance, parking, etc.5.

Generally speaking, with SFR or small multis, I just rely on the lease/rent roll (and some form of proof of payment; i.e. bank statements, deposit receipts, tax returns, etc.). 

@Jaycee Greene  they require a non refundable deposit and give 48hrs to see proof of funds 

Investor’s deposit will be used to make interest only payment for construction loans.

In mid February, many tenants get caught up when they start getting their income tax refunds (depending how fast they file).Income tax refunds also give tenants the needed funds for first month of rent + security deposit, so they can move.Check out this graph, which was created from tens of thousands of data points:Regarding your property, suggest the following:1) Where specifically is it being advertised?