It really isn't more expensive to convert a Fw to a SW reef, but you need to be positive that no copper medications were ever used in the tank, since the silicone sealant absorbs it. Copper is toxic to invertabrates (including anemones) and corals. You basically still need to buy all the equipment required for a reef tank, except for the tank and stand. It can save a couple hundred dollars. As far as "easy" anemones, a bulb tip
(Entacmaea quadricolor) is probably the best. They require moderate lighting (4 watts/gallon) and are generally hardy. The addition of a maroon clowfish will improve their chances of survival. If you decide to get one, I would recommend
www.LiveAquaria.com. They have very healthy livestock, and that is the first step in getting any animal to survive.