Sure you can use potatoes bought at the local market. That's what I do, and have had no problems to date.

However, you are assuming some level of risk by doing that. Potatoes are susceptible to viral diseases that can be transmitted through the tuber. The reason that using 'seed potatoes' is recommended is that they are usually certified as being disease free.

However, commercial growers generally use certified seed potatoes, so at most you will be one generation away from certified stock. Be aware, though, that a plant can be infected and it may not be obvious to the grower - some virus strains decrease yield but may not cause glaring physical changes to the parent plant itself, especially if the viral infection is not severe, so the grower of the spuds in your market may have had infected plants and not be aware. Again, some risk there, you have to weigh it up.

My situation is a bit like yours. I grow an autumn crop, which is long before the seed potatoes are readily available in the nurseries here. I've not had disease problems (that I'm aware of!).

I grew organic potatoes from Vitamin Cottage this year. The potatoes came from a Colorado farm. (I'm in Colorado.) They did fine. I also planted some King Souper's non-organic potatoes. They took longer to sprout and grow, but they did fine, too.

The only issue is if you want to grow potatoes vertically in a box or other container. Farm potatoes are bred for the roots to spread horizontally and produce potatoes at the same level as the original potato was planted. So, I'd suggest going with the flow and plan on this type of growth.

For information on growing vertically, check here: http://www.kenoshapotato.com/ . You will want a variety that does well vertically.

Here's my 2 cents worth:
This year has been tough so I couldn't afford to order seed potatoes. DS works at a grocery store so he keeps an eye on the mark down produce for me. I was able to get some yellow and red fingerlings marked down for $1 per package. They were green but I didn't care since I was planting them. I presprouted them and planted 2 20' rows for $2. If I could have gotten more I would have. The plants are amazing. Yes I now I'm taking a risk of disease but I made that choice.

I'll keep you posted on the harvest.

I also do this with sweet potatoes. I love white yams and once each year the store where DS works has them. I usually buy 2 for about $1.50 and start my own slips. Sometimes I'm able to save some from my harvest for the next year but not always.

I'm right with you guys, can't find seed potatoes to ship in fall, and too broke even if I could. I have potatoes I got from a local grower so I'm gonna risk it and try them. I figure it's better than nothing. At least I am trying. Which is more than alot of people do who don't grow any of there own food but cry about the cost of groceries. You just do what you have to do:-) Hope everyone's potatoes are successful!!