Loaning Private Money in an REO Foreclosure

I am looking for some advice on performing Private Money lending in the Chicagoland area.  I have a friend who is looking to purchase a property on the south side of Chicago, but I believe it is a banked owned property.  The bank is looking for a Cash buyer, but they do not have the Cash.

I would like to be their Private Money for this transaction, but I also want to protect myself to ensure that my investment is sound. I know there are a lot of factors to look at in this transaction, Fees, time, interest rate, etc. But I am thinking that a Promissory Note with property as collateral would make sense. Once purchased, the friend will put in the money to rehab the property , and then BRRRR the property to pay me back in 3-6 months.

Any thoughts on protecting my investment?  Does anyone know any lawyers in the Chicago area who have experience with this type of agreement?  Or perhaps contracts available on Bigger Pockets / other sources to get started?

Thanks

Matt