I have a chance to buy
 

a Singer model 15-91 in near perfect condition, with attachments etc. in cabinet. How much would this machine be worth? It is in working order. Not sure what to offer.

Fur, it all depends on what you are willing to pay. For me I would consider $50 my top dollar for machines with cabinets and attachments but I'm supper cheap. It also depends alot on your area for these things. Good luck they are great machines.

I'd say $75 - $100 with all those attachments.
You can't buy a new sewing machine that will work that well for that money. Go for it.

I bought mine in its original cabinet, all the attachments, etc. that came with it, and a bench with storage under the seat for $100. I felt that was good. It had been owned by the original owner only and had been well cared for. It is a treasure to me. At that stage of my vintage machine purchasing I wasn't quite into offering less to see what might happen. It doesn't hurt to offer a reasonable lower price. The worst they can say is 'no'. When I have offered less by $25 or more some have said, 'yes' and some have said, 'no'. Like I said, the worst they can say is no, then the ball is in your court. Have fun!

What is it worth questions are really not answerable... how common are they in your area and what you would want to pay is a big factor. And what is it worth TO YOU is the question. Personally, I don't pay much for vintage Singers. They are EVERYWHERE here.

Another thing to take into consideration, aside from availability, is the wiring. On most vintage Singers the wiring is going to need replacement. The cord set may look fine, but if you look at the wiring where it comes from the motor and light into the back of the electric connection on the machine, 9 times out of 10 you will find wires that are flaking, sticky from being exposed to grease from the grease cups, or cracked from age, and will have to be replaced for the machine to be safe. If you can do the work yourself - great! If you can't - not so great.

That's really good advice concerning the wiring! I second a good inspection. Congrats

Always good to check the wiring. However, there is plenty of great, knowledgeable help available here on this board both on how to check it and how to repair/replace it safely for safety! :)

I am thinking of getting rid of one of my machines too...pefect condition..I just wonder if people are really getting the prices that they are stating...even 100.00 when so many are giving them away for free...I have been asked many times if I want an old sewing machine and cabinets...wish I had the space but dont...