I bought those really really cheap $70 all foam (6'') single bed mattresses for the girls bunk beds and adore them. They are so comfortable! They have mattress protectors on them but I have taken on outside to wash and it did well. My mother still uses my 20 year old all foam bed from childhood and it is still pretty good feeling. A futon mattress is usually all foam I believe but probably more than $70. I don't where you live we got ours at a JYSK all rolled in plastic bag but Amazon has a "fancy" memory foam mattress for pretty cheap.
Yes, it takes a little while but it gets there. There was no smell to mine, though some people claim there was with theirs. Ive been pretty happy with it, for 150 bucks i don't think it can be beat. I ordered the 6 inch sleep master for my sisters kids, and while they aren't bad, they are definitely not as comfortable.
Thanks mrspolloco, that looks much more economical. This twin is only $104!. If I didn't cut it down, they could both lay on it no problem.
I'm not sure what you mean when you say "custom". Do you mean making a bed from scratch or something?
Everyone is different when it comes to beds. Some like it firm, others soft. Look on amazon and find the right one for you. Order a twin. Cut off what you don't need. A lot of people use mattress toppers or foam instead since its easier to cut, but those options may not be as firm/thick as you'd like.
I just ordered this mattress: http://www.amazon.com/gp/product/B005G02ESA/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1
I looked through the reviews and I knew it was right for me. One review said he was 300 lbs, and he couldn't even touch the bottom of the bed when he puts his weight on the bed with his knee. I like my mattress moderately firm bc of lower back pain. Some guy even asked "Can I cut this mattress to fit in my RV?" And another guy said he already cut his and its working fine. It's all about reading the reviews!
I'm not cutting mine, so I don't know the best thing to use for cutting. It doesn't need to be perfect since it will be covered by sheets. This guy sawed his off and then duct taped it: https://www.youtube.com/watch?v=72YLRVgejiE
Have a solid 100% latex mattress and I swear the guest bedroom twin is more comfortable. I like more firm though. You can get more firm latex but price goes up.
Here's the discounted latex info:
This is for the twin on amazon, they have different sizes. Look for certipure if you do go memory foam. (Its way different than the old tempurpedic days.)
We used this bed FJELLSE from from Ikea:
http://www.ikea.com/us/en/catalog/products/S59009824/
and these slats:
http://www.ikea.com/us/en/catalog/products/00160215/
Honestly if I had to do it over I'd buy a larger mattress on Amazon and the Ikea frame and slats. Just too comfy. The latex is dreamy but you have to trust you get the right firmness or you are stuck sleeping in a hammock like experience. That and the fact it weighs a ton. Good luck mattress shopping is fun!
Limited-time deal: Zinus SM-M-FMS-600T Ultima Comfort Memory Foam 6 Inch Mattress, Twin, Brown https://www.amazon.ca/dp/B005G02ESA/ref=cm_sw_r_cp_api_glt_i_dl_6EYEMW5QKTWPGXBEZMM4