Along with the things mentioned above, you're going to run into;
Lead paint issues.
Issues with the electrical... both units will need to be completely separate from each other, including panels and meters.
Issues with plumbing... again, both need to be separate, unless you're going to be dumb and include hot water in rent.
Issues with parking.
Issues with septic... it won't be big enough and will need to be rebuilt to be brought up to code.
When all is considered, I'd bet the numbers don't work. What would you get in rent if you renovated to make a great single family rental vs the rents from two less desirable, probably weirdly laid out, small units? Factor in the expense of gutting the house to the studs and converting to a two unit VS simply renovating and keeping it a single family and see what your returns are. I'm betting renovating and keeping it a single will cash flow better than the 2 unit approach.
When people rent a single family, they tend to think of it as their home, not just their temporary apartment, and will take better care of the place. They get the pride of "ownership" that doesn't come from an apartment with annoying neighbors and will stay longer too. I never hear of super long term tenants (10-20 years) in a multifamily, so you make out on vacancies and turnover costs too. I'm sure there's a metric you can find that will show you average stays in our area for single family rentals vs apartments.
Whatever you decide to do, the house will need to be deleaded if it's going to be a rental. The state law gives you 90 days from date of purchase to start the deleading in order to remove the liability of past tenents. Yes, you're responsible for past tenants that got lead poisoning there if you don't delead. The state basically changed the law to keep the liability with the property and transfer that liability from owner to owner until one deleads and breaks the chain. If you delead, the the past tenants can't sue you, they need to go after the previous owner. This is actually a good thing to know during the purchase... If it isn't already deleaded, it will have to be so it makes a great negotiation tool.
Assume around $5000 per unit and count the exterior as a unit, so $10,000 to delead a single family. Most come in at around half that, but if windows need to be replaced, or if the exterior doors do and need to be custom sized, it can get expensive quick, so $10k is a safe negotiating number. This will be the case for any property built before 1978.
If you want me to, I can run addresses through the database and see if they've ever been inspected. Often people get them inspected then don't actually delead, they just lie and check off unknown in lead paint disclosure. The state knows this happens, so every inspection goes in a state database so we can tell if it's been done or not.
If it has been inspected and not deleaded, you cannot renovate until a licensed deleader makes it lead safe and you get a Lead Certificate from the state. It would be illegal and get flagged as unauthorized deleading (UD) and you would NEVER be able to get a lead cert, only a letter of environmental protection which states you performed UD, got caught, then had to pay a licensed deleader to come in and fix it. This will likely increase your insurance and will tell tenants that you do illegal, sketchy, dangerous stuff with your rentals. Not the reputation you want!
Good luck on whatever you decide to do!!!
Derreck