First Purchase: Off Market FSBO. Where do I go from here?

[Jessica Sorensen]

Hey BP, I need your help again... I've found a great deal on an off-market property. The owner and I have come to a verbal agreement on the price, and he wants "a couple of months" to clear his things out of the garage & attic. (It's a rental, currently vacant but the owner was storing some building materials there.)  I'm happy to wait, but then I want this to be a sure thing in writing. 

How should I move forward with this transaction? I have been working with an agent to look at other properties (only one so far), but is it a good idea to involve him in this deal or save the commission by doing this with no agents? What contracts need to be signed (just a standard Purchase Agreement or more?) and where do I get those? I still want to do an inspection and I will be buying this house with a 20% down mortgage (pre-approved). Should I go to a title company and have them guide me through this? Lots of questions... I don't want to miss something I should be doing, nor do I want the seller to feel like I'm taking advantage of them in any way. (I worry that if I approach this with a buyer's agent, he'll feel the need to get himself a selling agent, and then a simple handshake deal just turned into a bunch of commission costs.)

Any advice is appreciated! This property is in California. Owner owns it free and clear. (He says... That's another thing I want to confirm.) Thank you!