I agree with much written above.
A few tips about the price point you are looking at... there are plenty of old American doubles in that range, but generally only in 12 ga. You'll pay plenty more for a nice 16, 20, or especially a 28ga.
Also decide early if you are ready to try double triggers. I really do like them, but find it hard to move back-and-forth between a single trigger and double trigger gun in the muscle memory moments of a hard flush.
You'll also find the majority of old doubles have at least one barrel with full chokes, which generally will not be compatible with steel shot. You might find good discounts on a 12 ga that has had then chokes opened, or barrels shortened removing a lot of the tight chokes. Generally don't shoot steel in any choke tighter than M. Also investigate the chamber lengths... there are a lot of 2.5 inch 12 ga. guns out these (esp. English or German) that are really tough to find non-toxic (or even lead) shot for right now.
And don't ignore the suggestions by MT_DD_FAN above. I really like the CZ Bobwhite 20 ga I bought several years ago for <$600. The wood is always plain, the metal lacks character, but you can shoot anything thru them, change chokes, and test your preferences for double triggers. I've traveled the world with mine.
