The Obtain Familiar Feat makes the Sor/Wiz class feature available to anyone because "familiars can be useful allies for characters of any class. Rogues can use a clever raccoon or crow familiars as an extra pair of hands or eyes in their work (to say nothing of having an ally to help them get out of tight spots). A performing animal can be part of a bard’s act. Clerics might have familiars sacred to their deity, while familiars for rangers or barbarians can serve as guides, companions, and helpers in the wilderness." - Dragon #280, p62.
Accordingly they have the normal familiar benefits/limitations, including being limited to have a single familiar. However the same issue has a number of interesting feats including Extra Familiar which specifically allows you to acquire an additional familiar each time you take it. I highly recommend acquiring a copy if you routinely deal with familiars as it adds several new base animal species as well as a number of highly useful feats.
"EXTRA FAMILIAR
General
You have an additional familiar.
Benefit: By taking this feat you get an additional animal familiar of a type described in the Player’s Handbook (or this article, with the DM’s permission). This familiar can be the same type of animal as your first, or a different type. Existing familiar feats apply to the new familiar. So if you have the Construct Familiar feat, for example, the new familiar you call can be a construct. The sorcerer or wizard gains all the benefits of both familiars, but identical bonuses from multiple familiars don’t stack. For example, a wizard with both an owl and a cat familiar receives only a +2 bonus to Move Silently checks, not a +4 bonus.
Special: A character can gain this feat multiple times. Each time you take the feat, you can call another familiar." -- Dragon #280, p62