I agree with the others here who say MF is better than SF. When your SF is down for renovation or being marketed for a new tenant, you have $0 coming in but you still have a mortgage to pay, so the month is automatically in the red, not even counting any other expenses, etc.. When you have MF, even if it is just a duplex, you have some $ coming in that month that often will at least cover the mortgage. Not to mention that the income of 2+ units share the cost of roof replacement, lawn mowing, property taxes, etc.
I even think of when it may be time to replace windows down the road (or right away).... with a SF you will have windows on 4 sides of the unit, whereas with a duplex you will have only 3 sides & could be fewer for 3+ units. In my market (Columbus, OH) a SF next door to a duplex unit isn't going to rent for dramatically more in most areas, assuming similar factors of condition, sq ft, etc.. We decided long ago that we won't even consider a SF rental simply because we want to avoid ever having to make a mortgage payment out of our own pocket if possible...
That all being said I know there are people out there who prefer SF so it really is just about figuring out what works best for you. If you need any help in Columbus, feel free to reach out. Best of luck to you!