I just want to add: Whether the buyers plan to re-sell the place right away (flip it), or not, is absolutely none of your business.
If you are focused on anything that's irrelevant to your deal--including the possible profitability of a buyer in the future, what color they want to paint the inside, the fact that they hate the way you re-did your kitchen--then it really is too bad you don't have a broker, because to sell property as an owner (and I've done it), above all, the owner/seller has to be pure business and focused on the task at hand.
Readers who follow my posts know I am not one of these people who pushes agents/brokers at every opportunity--absolutely not. But here you are, selling your own place, and you're posting anonymously on Trulia to ask what to do when someone makes you an offer?? Of course it's your decision, it is your property. But you sound like the kind of person who risks gets taken advantage of, or not selling at the highest possible price, which could mean less money in your pocket than if you had had a broker working for you.
Karla Harby VP