Hi Tarrycat
Sword blades, and particularly Japanese swords, due to the romanticism and pop culture fascination, have become a large industry catering to a huge variety of customers.
They are typically grouped into broad categories, labelled according to value, cost or production quality/method. Which you would want is entirely dependent on the intended purpose. As you've said you have no knowledge, I'm assuming that you're not training in a Japanese sword art? If that's the case, I'd imagine that you'd want one either to simply hang on the wall (funnily enough one of the categories I referred to earlier is 'wallhanger'), or just to do some backyard cutting?
Wallhangers come in many shapes, sizes and materials - but are characteristically cheap, often stainless steel (not a good steel for sword blades) and poorly/cheaply finished. Typically the
hamon (often mistakenly called a 'temper line') is artifically etched on the blade, and they often feature gaudy, shiny fittings and can be visually quite dramatic, as the intended purpose is to simply look flash hanging up on the wall. NOT to be used to actually cut anything.
A wallhanger:
Another popular category are Chinese forged blades - slightly more expensive (typically) than wallhangers, they are being pumped out of forges/factories in Longquan. Wildly variable in quality, these blades may sometimes be appropriate for light backyard cutting, but also.. may not be. One of the more highly regarded of these is 'Huawei swords' who sell on ebay and alibaba. While the fittings are not much of a step up from wallhanger level, the blades are T10 (also called W1 - high carbon tool steel.. much more appropriate for swords), differentially hardened and therefore can be used.. with great care.
A huawei:
Beyond production blades, you may contract a bladesmith to forge you a sword. A bare blade made by a Japanese smith from tamahagane, in the traditional manner, will start at several thousand dollars. There are western smiths like Howard Clark who forge swords from modern steels like 1084 and L6 - one of his bare blades starts around 3k and has a couple of year wait list IIRC. Of course, these bare blades then need to have tsuba, tsuka, saya and koshirae built to fit.. another several thousand minimum. Fully finished, 10k is cheap in this category.
There are forums out there aimed at sword purchasers - they may provide more specific info. Whatever you end up doing - please take great care in handling any sharp sword.
Phew... that got pretty long.. I hope it helps