We have and we just do a double deposit. 

My question is can I secure a deposit/holding fee from them 2 months out to hold the property for them. 

You also have to realize that even if you are not using the entire heloc limit "Some" underwriters still calculate the Maximum payment into consideration.There are some ways to pull money out of a Heloc and deposit it into a savings/checking account prior to application to satisfy the PITI reserve requirements.

Can I pro rate the week and deduct this from his deposit?

FHA doesn't allow this.How is it possible that FHA didn't account for security deposits and prorated rents?

Unless you need to sell and have no other interest I would only accept with their earnest deposit being non-refundable.

Hi A potential tenant of mine who looks really good on paper (credit score, income and else) is asking if we can take rhino policy for security deposit ? 

I have received a lot of feedback from travel healthcare workers who say "It is terrifying to send a deposit (+1 month rent sometimes) to a stranger to hold space when it could be a scam".

Some of these small contractors are basically bankrupt day to day, taking your deposit to finish the last job. 

You could also look at interest rates and monetary supply, interest rates probably are not going anywhere until monetary supply comes down - but in speaking with some banks they are losing money month over month on deposits which really hurts banks.So a lot of moving parts in the economy, all I will say is people need to understand what happens if things get better or get worse.