too many people try to make money on old bikes. Another way to approach it is

"hey , look at the cool bike I created from a bunch of old parts. "

These days I am into the artistic aspect of bike building. If its rusty buy a cheap sand blasting kit and strip off all the paint then get out the Rustoleum and give the frame a killer paint job.

Take it completely apart before you do anything else. Check the frame for dents and cracks or crash damage.

Take all the small bits and throw them into a gallon of white vinegar (clean the gunk off first with a tooth brush and some wd40 or paint thinner). They will come out shiny like new. If you can set up a polishing wheel Polish the heck out of any bright work that is not anodized. Clean those aluminum wheels and axles. Color coordinate with bar tape and cable covers, accessorize with some hammered fenders.

Make it special. Buy a decal with your name or the persons you are building it for and put it on the down tube. Put some Kenda gum walls on it for a classy look.

Do all of that and you will have had a good experience and will have created a thing of beauty like the bike shown below that you won't want to sell. If you give it to someone they will love you forever.