Lease option help/House Hacking

[Zachary Bouck]

I just recently moved into (half of) a duplex and when touring the place for the first time I struck up a conversation about real estate with the landlord(A habit that I learned from someone here... such good advice: Talk about real estate with EVERYONE). He mentioned he was starting to consider offloading the place and would consider a lease with option to buy, even crediting some rent towards the final purchase price. I told him I was seriously interested, but I don't know where to go from here. Some details about the house:

- Lansing, MI Area, Neighborhood(REO Town) kinda shady but nice.

- SEV is $38,500, Zillow has it at $108,838, so I'm thinking fair value around $90k?

- Built in 1920, 2474 sq. ft(whole house)

- Taxes are about $2700 a year

- Rent for each side is $875, although looking at the neighborhood, that's due for a raise soon.

- There is $227.83 in taxes owed from Winter 2015

- Our side seems in pretty okay condition, nothing major that we've noticed. Know nothing about the other side except that the tenants living there have been paying rent on time for ~20 years and probably aren't moving any time soon.

I really want to at least get the option(2-3 years) on the place soon as I love the idea of house hacking, and we can use the next 2-3 years to build our credit so we can get a good FHA loan. Whether or not we actually end up buying it during the option period is another matter.

What's my next step to get the option finalized? We've already signed the lease for a year. Do I get an attorney involved? Should I find a realtor? Is there just a blank one online I can print out and have us fill out and sign? 

Thanks in advance!