Eligibility for Social Security Disability Income (SSDI) is determined by a combination of factors including your age, education, work history and your impairments.
For a younger individual (under 50) you would have to show that you were able to perform "less than sedentary work" and that you are unable to perform your past relevant work (all work where you earned $1000 per month for the lat 15 years).
Rheumatoid arthritis and fibromyalgia can both be considered "severe impairments" for SSDI purposes. Whether you are disabled depends on the severity of your impairments. SSA will look at your medical records from around the date you say you became disabled. Based on what you have described, I certainly think you would qualify based on your RA.
Here is the specific law that relates to inflammatory arthritis, the listing details what you would need to show to win based solely on RA: http://www.ssa.gov/disability/professionals/bluebook/14.00-Immune-Adult.htm#14_09
You may also qualify under the Lupus listing, or other Immune Disorder listings: http://www.ssa.gov/disability/professionals/bluebook/14.00-Immune-Adult.htm
Fibromyalgia is not an immune disorder for SS purposes. It is typically treated by a rheumatologist, and in order to show you "have" fibromyalgia, you need to show a history of at least 11/18 trigger points, the American College of Rheumatology criteria for a positive Fibromyalgia diagnosis.
As for what you would get, that varies depending on how much you have paid in. For some people it is only a few hundred dollar per month. For others it is a few thousand. $1500 to $2000 is probably average, but it is based on an incomprehensible algorithm... so I can't tell you what you will get monthly. You get a notice in the mail every year telling you your disability amount.
As for how long it takes, that depends upon what stage your benefits are granted. If you initial application is granted (about 25% are granted) you will be receiving benefits in a few months. If you have to go to a hearing, it can take as long as 2 years. While you wait for your hearing, you cannot earn over $1000 per month. If and when you win your case, you will get back pay for those months.
The final issue is your taxes. The government may withhold your benefits to pay your tax bill. So you will need to continue sorting that out.