Buying any property you rent could be a windfall, however, you have to carefully evaluate many factors, among them how the purchase fits into your long-range financial goals, and how the purchase will change your present expense picture.
Buying directly from the homeowner poses a few challenges, but it also presents some great possibilities in the resulting buy/sell agreement. Challenge, separating the "friendship" (if this applies) from the business. While it may fit well for Pacific Bell to tout that "...the best business calls are personal..." making a major purchase, like a home, should never be left to taking things for granted just because "what will s/he think if I ask this or that..." Some of the biggest mistakes are made because of putting too much emphasis on trusting someone or something more than your best judgement may dictate. That said, you need to weigh the pros and cons carefully as they impact you. Sure an exceptional opportunity may have just landed on your lap, but don't take someone else's word for it without doing your due diligence.
What should you consider beside the way this buying decision (versus renting) will affect you present financial profile? Here's a brief (partial) list:
Is this place you truly would like to call home (for the longer term)
In a condo, be sure to study the condo complex's history, finances, governing board, policies, dues, proposed assessments and even the minutes of the meetings. If you can't get a hold of these important documents, think twice about making this sort of purchase.
Are you getting a better than market term or price?
Remember, you don't want to buy someone's headaches.
On the positive side, it is easier to get into a direct purchase from an owner -- you won't have to deal with competing offers, for instance.
Do plenty of research, and talk to a Realtor who'll talk to you without just looking for another pay day. What you need is honest, unbiased analysis, and any great Realtor may do that, but remember, Realtors earn money for putting buyers and sellers together, and usually get paid by the seller, unless you decide to retain one for your own sake.
I know you probably want a little more factual insights, but, you didn't give enough details or your circumstance to give you all but the most generic observations. Hope this helps.