Very first lease option - advice?

[Stephen Thatcher]

I'm new to REI. I bought my first property in September 2018 using a HELOC. It's doing well. I'm able to rent it out to a government employee for $166 a day. My question, however, concerns my next deal. I approached a seller about using a lease option to purchase his house. I really couldn't believe that he accepted the offer. I had to contain my shock. He had it on the market for $132,000. I knew it would probably appraise for more. My realtor was nice enough to do a comp for me which came in at $140,000. I offered him $135,000 with $1,000 option fee with a four-year option. I can rent out the house for $1200-$1300. I would pay him $1,000 a month and the $200/$300 would go to me. I was completely upfront with the seller and disclosed what my plans were for the house and explained the screening process for possible tenants.

I feel like I'm doing something wrong though because it seems way too easy. Does anyone see anything that I missed or something that I need to research? And what's my next step? Do I go talk to an attorney to draw up the papers? Do I need to get a CPA in on the deal as well? We're not finalizing the deal until Feb/March 2019 but I'd like to get a jump on this since it is literally my first rodeo with a lease option.  

Thanks in advance.