Like pretty much everything else in life, build quality and features in pontoon boats vary considerably and are usually proportionate to price. I assume that like most folks here, you aren't interested in spending your hard-earned disposable income on lesser quality gear, especially if after a short time using it, you discover that you should have spent a bit more and bought a boat with better features or build quality.
IMHO, there's a large gap between most new boats in the $350 range and those costing twice as much. (I know you said you had $400 to spend, but buying a new boat means that your purchase will also be subject to our state's nearly 10% sales tax. Walking out the door spending just under $400 means you'll need to buy a $355 boat assuming 10% sales tax. And don't forget about add-ons like fins, anchor, Oar-Rites, boat bags, rod holder, pump, etc. None of those are usually included with a new boat, so you'll need to spend even more before you're ready to fish.
May I suggest that your money will go a lot farther if you look for a pre-owned pontoon boat instead of buying one new off the shelf?
Pontoon boats are regularly offered in both the WFF classifieds as well as on Craigslist. For example, a friend patiently waited to buy his 'toon until he found a used Buck's Bags Southfork on Craigslist. Not only did he buy a $750 msrp boat with stainless steel frame, anchor, fins, pumps (2), Oar Rites and a rod holder, he got the whole package for just $300.
Just sayin' . . .
K