The experts will likely say no.
It's better than spending money on cars and cable TV, but at first blush, I'm not convinced the numbers will work well for you, and I'm more willing to give real estate investments the benefit of the doubt than a lot of people here.
You don't have to answer these questions out loud, but my initial thoughts - why do you have the opportunity to buy this property below market value? How do you know the tenant situation is as rosy as it sounds? Is this a family situation (to me, family considerations can certainly trump financial ones, but they can also be problematic)? Why is the seller getting rid of it if they are cashflowing and the property is likely to appreciate?
As for raw numbers, you are looking at about $40k cash up front investment. Cash flow is $3600 per year based on what you've said. If we pretend no maintenance, no utilities, no chance of vacancy, no management costs, no depreciation of property, no time/money to manage the rental then it sounds like 9% return on initial investment which is pretty good, especially if this is a "good neighborhood/good market". That of course doesn't include equity growth, depreciation, or tax benefits, which may work further in your favor. There are also opportunity costs of tying u your money and losing out on better investments.
And there are costs which will eventually come due (many people assume 50% of your monthly rent will go to expenses. This is crude, but something to consider). Add in maintenance (assume 1% per year conservatively is $2000) and you are down to $1600 cash flow per year or 4% return on initial investment (not counting inflation). Eventually, there will be vacancies to account for. Would you pay any utilities? I assume no HOA. What are the odds of missed rent payments based on the tenants' financial situation/future? Is income for the tenants guaranteed? Could they become insolvent if one of them gets ill and needs nursing home care? In America, the only way many people get that covered is by impoverishing themselves until they qualify for Medicaid, meaning they may not be able to pay rent. Would you throw out an elderly tenant with a spouse in a nursing home? Anyway, I'm not saying no outright, though I wouldn't disagree with anyone who said that the return isn't worth it. But, I think there are many other parts of the story to consider before you could convince me to entertain a yes.