I've read that I should open a business savings and checking at a local institution - particularly for the security deposits.  

Many lenders will require a 12 month lease to be in place along with the security deposit and first month rent collected. 

@Carl Rowles we screen all tenants exactly the same, but know several of our local competitors cut corners to attract more S8 applicants - waiving application fees, security deposits, etc.You can try to weed out applicants that have poor "house maintenance" skills by doing surprise zoom calls and asking them to show you their kitchen, bathroom and another room.

It also means that your renters will want to vet their subletters carefully to ensure they get their security deposits back, etc.

I chose to forfeit my deposit and walk away from the project.   

You could also consider a small security deposit as well.

I am leaning to saying no but I may ask for additional deposit PLUS additional rent.

You'll also need a way to collect your security deposit(s) and rent.

He wants to get back on the property ladder and we have talked about me putting in 50% of the deposit needed to purchase a house.

Mainly, you'll want to let the potential partner how much of the contract deposit you'll be contributing.