Answer this---how long will it take you to sand--stain--varnish that?
What will the stain,sandpaper,masking tape and varnish cost? Can you do more than one in a day?
More than ten?
What is your overhead? Selling time? Gas /car payment/insurance/phone tool expanse ?
How much do you need to take home in a day?
After you are paid--how much will be left to grow your business? (hint--buy a painting estimating book)