Do i need hip replacement?

Im 20 yrs old have had rheumatoid arthritis since i was about 12 and my hip use to hurt. But after many yrs without a problem the pain suddenly came back a few months ago and really hurts after i walk or stand for a while and feels really stiff. I believe I do or will need hip replacement but my insurance doesnt kick in untill august so i cant have xrays or anythin till then because i cant afford it I can barely afford my dr appts. I just really need some info if i do or dont need or how much it is and afterwards what kinda work can i do will i have to have a career behind a desk ?

Before you jump to conclusions about possible treatments, you need a complete assessment of your hip and a professional opinion of what it will take to fix it or at least enable you to better handle the pain. When you are in pain, even waiting until August seems unacceptable. Some possibilities that may help your symptoms: daily NSAIDS (check with your doctor first because even though NSAIDS such as Aleve, Motrin, etc. are sold OTC, they are not necessarily benign drugs to take on a daily basis); walking aid - could be a single crutch or even a pair. This will alleviate your pain considerably because you will be taking weight off that sore joint. It will make your days much easier. Another possibility: a program of exercises designed to strengthen the muscles around your joint. This may or may not help much but it's non-surgical, cheap, and worth a try.
What you describe sounds like classic osteoarthritis. But don't take my word for it. Fortunately it is pretty easy to diagnose osteoarthritis from an x-ray which isn't very expensive.
As the other answers have indicated, 20 years old is very young to even consider hip replacement. But I know of 2 people who had THR at 18 and 17 yrs. So it isn't unheard of.
As to the kind of work that you could do after a hip replacement (this is really getting ahead of yourself) sedentary work isn't the only choice and may not even be the best choice. I (who had my THRs when I was almost 3x your age) consider that I could have gone back to be regular job at about 2-3 months. It required a variety of activity - standing, walking, and sitting. This worked out great as I would have had trouble sitting at a computer all day. Now that they're healed, I can walk miles, take no pain meds, have no stiffness or pain, and generally lead a pretty normal life for someone my age. I avoid high-impact activities and do not lift and carry heavy loads for long distances. I avoid these things to prolong the useful life of my fake joints.
The problem with putting hip replacements in young people is that they tend to be much more active than us oldsters and to put it bluntly, they (especially young males) are likely to trash their fake joints and need revisions sooner. The idea is to get the joint to outlive you and that's really hard when you begin at a very young age. REvisions are less successful than primary THRs, they have a higher complication rate, and a hip cannot be revised ad infinitum. Eventually you might run out of bone to hold the hip prosthesis.
And, to the last part of your question: how much does it cost. While costs vary in different regions of the US (and seem to rise every year) I can tell you what mine cost 5 yrs ago. For each hip, the hospital bill was around 18k - and all the other stuff - surgeon fee, physical therapy, misc. such as drugs, dr. visits - probably brought the total to around 25k. Keep in mind that this was 5 yrs ago in a small midwestern city.

They won't fix your hip yet you are to young. Perhaps you have something painful like bursitis (it is painful) mostly at night.
Have you tried some form of exercise like pilates?
Or Yoga -swimming??
How about a memory foam mattress cover - and taking something to help you during the day for discomfort.
Such as advil or Alleeve.

It could be something as silly as your mattress - and add something in to your exercise regime if you have time - simple stretching may help.

I've recently had hip replacement surgery. I have both rheumatoid and osteoarthritis. The surgeon charged $9,000 and the 3 day hospital bill was over $25,000. The stabilizer muscle at the side of my hip was badly damaged before the surgery and it had to be cut in two in order to replace the hip. Now I am not able to walk without a mobility aid, possibly forever because of that muscle. I was told that after three months post-op, I could return to regular activity but it's not happened for me. I cannot sit in the tub, (can't get down or up); I now have tendonitis in my elbows from leaning on the walker. I would say I've had several very painful procedures but the hip surgery was by far the worst! Ask lots of questions before you decide to do it. You will not have to have a sedentary job. I know one man in his 60's who had hip replacement 20 years ago and he rides horses, repairs cars, and is very active. I also know a man in his early 80's who had the surgery two years ago and walks four miles a day. So there are many success stories. But I've had problems so I encourage you to learn all you can before you choose the surgery.

At 20, you are not a good candidate for a THR. They say a good THR lasts 15-20 years. So at 35 or 40, you will need revision surgery already. And after another 15-20 years again? Good if you need revision only for loosening. If your hip gets infected, kiss the 15-20 years longevity rate goodbye. You need to delay the surgery as long as you can- your orthopedic doctor is the best person who can help you. He should consider your age, the amount of pain you have, and the amount of joint destruction there is in your hips before doing surgery. If you are not getting these assessments, look for another doctor.