Lease option deal/advice

I'm new to lease options but have an opportunity to make an offer. Owner is desperate to sell but owes about what the house is worth. Roughly $160K. Not exactly sure how I should approach it. Thinking about offering $160-170K purchase price on a 5-year option with no option fee and offering to pay his mortgage which is roughly $1200. It's not in a great area, it's a single family detached and an agent believes I can lease it between $14-1500. I would lease it with a $3-5k option fee. As you can tell my numbers are all over the place because I have no experience with options and haven't laid eyes on many structures of these deals. Any help would be greatly appreciated.