I looks like possibly a White Rotary sewing machine, though it is in a Singer base. To some people anything treadle is a Singer. Age is difficult to determine, but the serial # and brand might help. As is commonly said- the worth is whatever you are willing to pay. Check your local Craigslist for sample prices- ignore anything over $100. Be sure whatever you buy has the shuttle and at least one bobbin, and hopefully some attachments and needles. Instruction manuals can be found for free online. Be sure the machine moves freely when you turn the handwheel.
To bring one home it is advisable to remove the machine from the base to avoid a disaster of tipping over or falling off the hinges and smashing the case. It may just lift off the hinge pin when tilted back, or need to have a tiny slot screw underneath pinning it that can be easily unscrewed without removing the hinge from the base. Lay the base down in the car and prop it to avoid it slamming into the back of your head or breaking out a window. Dump everything out of the drawers into a cookie tin or something to be Sure you aren't bringing home mice to nest in your car vents. Very expensive to deal with! Watch out for razor blades. Head on over to the vintage and antique section of the Board for lots of friendly help.