I like sleeping in a queen even though I'm the only one in the bed. My current one I got before Covid. I went to a mattress store and tried it out, and they threw in the bed frame for free. I got an adjustable bedframe, so I can raise the head a bit. This helps because with my allergies I tend to cough a lot if I lie flat.

Most places that sell mattresses in the US will work out a payment plan for you if you can't afford to pay for everything up front.

I just tried to find my receipt from when I got the mattress and frame in 2019, but I can't. I spent somewhere between $1000 and $2000 on it. Because I have good credit, I was able to get an interest free payment plan and paid it off in 6 months.