if you are buying an existing tank, it will still go through certian stages, and most are not good for an anemone, just because all the water and rock and sand and filters and everything is saved and used, it will not be perfect right off the bat,
and as i said anemones belong in the wild, they are beautiful crtiter, with very specail needs, and are even more delicate, they have almost no chance of survival in an aquarium, and someone telling you that theirs lived for 6 months, or a year, or even 2, still have not kept an anmeone long, very few have kept them for years, and they should live for more than decades(even over 100 yrs in the wild) and most of us reefers are trying to keep our critters for life, not months, just because the lfs says that they did good in doing so, we want long lives(years or even a decade or more for our fish even)
MAY I offer another suggestion, clowns often take to soft corals too, and as for the anemone, not only do you have my feelings, but here is some info, it is hit or miss, most clowns of one species will generally like...., but your odds are about 50/50 of them even wantin ga host at all, especially if they are tank raise(IMO), and i could preach for hours about buying tank raised clowns, jsut to push against the use of cyanide,and very hard, but the fact is that clowns will do very well without anemones or any host at all and there are alternatives to the anemone
sorry if i sound one sided or forward, but i feel strongly about this, and feel that all newcomers to this hobby should take a good look at the reality of certain things, that your stores won't ever tell you(because either they don't know, or don't want ot know, or don't want you to know)