Earl, the only way to make a living in this business is to treat it as a business. You must first and foremost keep meticulous records of your expenditures. There are more than 1,200 legal deductions that are available to a self employed musician/singer/entertainer. Things you don't even think about are often fully deductible.
A dear, departed friend of mine once told me that if you are out on a job and have to take a crap in a pay toilet, write it down. That $.50 cents you paid adds up at the end of the year. Of course, this means you will be filling out a schedule "C" on your income tax return, which requires lots of time and effort, but by the end of the year, you will get to keep most of your earnings.
The downside of this is you must keep all those receipts for 7 years, which is a safeguard in the event you get audited. Consequently, you will have boxes of receipts stored in the attic that you forget about after a few years and the mice tend to find those box contents make great nesting material.

As for the age thing, don't worry about it! I was playing and singing to the spring breakers down in Marathon Key, Florida just two years ago, when I was 76 years old. The ladies were all built like Barbie Dolls and ironically, the most requested songs were anything Sinatra, Jimmy Buffett, Zach Brown, and ZZ Top, stuff we have been playing and singing for years. The only reason I retired was health issues I could no longer ignore or cope with.
Good luck,
Gary

Hope this helps,