You said it was a single family home. How do you know that? Did the sellers tells you that is was a single family home? You really have to be careful. One of the first things you ever and always want to do is find out if the property or building you are looking at is a being used legally and is zoned and permitted for that use. In other words if it is zoned for and permitted as a single family home then that is what it should be used for and if it is zoned as a multi family unit that is what it should be being used for. You do not want to buy and pay for a single family home thinking you have just bought a multifamily unit and have prices it as such. That would be my first red flag.
If you do not already know how you should first learn how to examine deeds, tax records, zoning for the property, assessors records anything and everything that will tell you if what is there is a legal unit and zoned for its current use. Learn how to find out when it was last purchased and sold and what the price was. Learn how to obtain comps for the area and that particular property. If you intend to be the buyer/owner you might consider finding an buyer's agent to work with you.
One indication that you may not have a legal unit on a multi unity use building is to see how many meters there are on the property. Usually if the units we constructed legally from the start there will be independent metering for each unit, a separate gas, water, and electric meter and there should be two addresses, one for each unit. If you see only one address then that would put up a red flag for me also.
These are just tips and do not cover all the things you have to make sure of. Study more, learn more, ask more questions, and try to net work with other investors who have more experience and can guide you further. I always recommend to new investors to consult both a real estate agent and a real estate attorney until you learn how to actually due the due diligence properly and effectively on you own.
Owning real estate can be a very positive thing for your life but is can also present many real dangers so learn to protect yourself and take that part of if very serious.
Is there an existing mortgage on the property and if there is can you verify if the mortgage is against a single family unit of a multifamily unit. How about the insurance on the property is the policy for a single family unit of a multifamily unit?
You may like the lay out and be thinking you are buying a nice multifamily unit and be able to generate income at a certain level or perhaps live in one unit and rent out the other thereby getting financially assistance to pay off your mortgage if you plan to finance.
Do not buy problem properties no matter how tempting it may seem to you. Part of your system to investing in real estate should be to implement, " Risk Management".
I can't tell you what to do or how to do it but I hope you find these tips helpful.