Hi mattressseeker2014,
Choosing a mattress for a guest bedroom or for temporary use that is used less frequently and doesn’t need to “match” a specific person is generally a little easier than choosing a mattress for a particular person where PPP and durability are both more important.
In very general terms a good strategy can be to buy a basic “medium” to “medium firm” mattress (firmness ratings can vary from manufacturer to manufacturer but as long as it’s in the general range it would be fine) which many people would be fine with at least temporarily and then to add a topper so that your guests that prefer a softer mattress can add the topper. You would only need materials that are in the lower end of the quality/durability range in post #4 here because a guest mattress will last longer if it’s only being used occasionally than it would if it was being used every day. I would still avoid materials that are lower quality than the guidelines because even with temporary use there they can still soften or break down too quickly. With a good quality topper though this strategy may take you outside your budget range because of the additional expense of a topper. If you do decide to go in this direction then some of the better online sources for toppers I’m aware of are listed in post #4 here.
Another good strategy can be a component mattress that uses good quality materials where you can rearrange the layers inside the mattress to change the comfort and/or support for different guests. (such as the 12 in 1 customizable here).
Some of the better online options I’m aware of that are in lower budget ranges are linked in post #4 here.
The better options or possibilities I’m aware of in the San Diego area (subject to the quality/value guidelines here) are listed in post #2 here.
This would certainly make a good quality/value choice. The 1.5 lb base foam would be fine for most of your guests that are in the low 200’s or lower and also wouldn’t be a durability issue with temporary use for heavier guests as well. I would choose a more “average” firmness in the medium range but Dreamfoam would be a good source of guidance for firmness choices as well.
Ikea also has some good quality/value options in a lower budget range that would be suitable as a guest bed.
If you are planning to order from Foambymail (FBM) then I would read this post and this post and this topic (about their polyfoam and sources) and this post (presumably from a past employee) before buying anything or considering them as a reliable supplier.
I’m assuming you mean northshorelinens here (in Vancouver). They sell some good quality latex mattresses but as far as I know all the mattresses they sell are outside your $500 budget range.
As you probably know they are one of the members here which means that I think highly of them and they would be well worth considering as well if they carry any mattresses that fit all your criteria (they don’t list their prices on their website).
Phoenix