Lenders are much tighter today than a few years ago. I did sell a 2-family property that had a long term tenant who had been in residence for several years. The lender did count his rental income in the income and debt ratios. If you buy a vacant duplex/2-family chances are the lender will determine qualification based upon only your income and not provide any allowance for rental income.
I am hesitant to recommend lease-options or lease-purchases, although I have done them, and in rare circumstances, even recommended it. Usually, a word of caution is in order. Most options do not materialize and the renter forfeits option monies.
Buying a 2-family, or taking in a roommate can be a good solution. Make sure that you budget for vacancy and have the ability to make the payment the months that you may not have rental income. You still must be able to qualify, and without making your rate go so high that it becomes a poor financial choice.
There are some motivated sellers out there, both in resale and new construction. If you are flexible on your housing choices, you can shop for the best deal and motivated sellers. If your goal is to buy a place and manage your finances well, focus clearly on that goal and be a bit more tolerant of funky wallpaper or older appliances. A mediocre property in a fantastic location is still a winner most of the time.
Find a good buyers agent, let that person know that you will be loyal to them and what you expect from them. If you do not already have a lender, you need to find out what you can really buy before spinning circles in the wrong direction. A buyers agent may help you find a lender. Or if you find a lender, he or she may lead you to a great buyers agent.
Best of Luck!