There isn't much out there in that price range that is worth having long term ...they're expensive to make ( if they're built right ) .../ and they have so much drop at the comb / and the length of pull on many of them is so short ...a lot of shooters can't shoot them without some significant modifications to the stocks (or at least I can't).
Traditionally they were built for a different style of shooting - that was more traditional in Europe than the US ...but if they fit you they can be fun.
A SXS that is well built/and is a good solid gun - to give you some perspective is the Browning BSS ( Browning Side by Side) that was made from 1978 - 1987. There are quite a few of them around / they aren't really in the collectable category - like some of the older american or english guns ...and reasonably affordable at around $ 2,000 for a good clean one / although I've seen prices from $ 800 to over $ 5,000 on really nice ones.
You can do a search on gunbroker ....for shotguns / then put *BSS into the search category and current listings will come up on the BSS's - but you might find one with fixed chokes / that's been beat up a little in a local shop - that you can clean up / fix up and make into a nice gun for under $1,000.
The Turkish and Russian imports have all kinds of issues - barrels that are not regulated properly and not hitting the same point of impact / trigger issues / parts issues, etc ....
Expensive SXS's ..... Fox, Purdy, etc ...are priced at levels way above the Brownings for the most part. Beretta still makes a SXS in their field gun series - that retail new for around $ 3,500 and they're decent guns as well.
http://www.berettausa.com/shop-by-de...side-by-sides/
But the reality is - $ 3,500 for a new SXS is about what you'll have to pay for a good gun / $ 1,000 - $ 2,000 for a good used one probably ... / and I'm no expert on the older guns from Fox, Purdy, etc ....some of them can be purchased cheap ...but you're going to have to know what you're buying and whether it needs to be checked by a good gunsmith.
Even good used Over Unders ...which are less expensive to make than SXS's ---- used entry level guns, not fancy by any stretch of the imagination, from Browing or Beretta ...like the Browning Lightning series made in the 1980's ...will cost you $ 600 - $900 ....for a very serviceable gun these days....
Rather than buy a $400 gun that might not hold up / or has all kinds of issues ...I'd say save your money until you can afford to buy a decent long term gun ( that might even go up in value as you own it ) ...or consider a different platform if your budget is limited to $400.