Hi URSTECH,
I would make sure you’ve read the mattress shopping tutorial here which includes some basic information and guidelines that will help you “get up to speed” about the type and quality of the materials to look for and the type and design of mattress you want to build.
If you are thinking about designing and building your own mattress with your own separate components then I would also read post #15 here and especially the part under option #3 and the posts it links to.
That depends on the type of mattress you build, which mattress you are “targeting” as a blueprint, where you source your layers and components from, and on how many “mistakes” you make before you find your ideal configuration.
jankdc provided a link to a list of the better DIY online suppliers I’m aware of. There may also be some local options in the Baltimore list here but I doubt that any of them would be in the same budget range as the online suppliers in the list. http://www.house-of-foam.com/ may also be worth a call or a visit.
That would depend on the size of your mattress, on the type and thickness of the layers in your design, and on the type of cover you choose. You are probably in the budget range where good quality polyfoam is reasonable but your budget is almost certainly too low for good quality memory foam or latex in a suitable design (except perhaps in fairly thin layers).
I would make sure that all of these meet the foam quality guidelines in post #4 here and that you know the foam density of all the layers before considering any of these. I would also read post #6 here and the posts it links to along with this topic before considering a Lucid mattress. A forum search on Lucid (you can just click the link) will bring up more information about them as well.
Some of the better latex or latex hybrid options I’m aware of that are in a lower budget range are listed in posts #3 and #4 here.
Some of the better manufacturers or retailers that have memory foam or polyfoam mattresses in a lower budget range are listed in post #4 here.
Phoenix