The rules explicitly make mention of helping in town (if you keep checks going into town, you can only use them to get xp for help rolls.)
Is there any Lifestyle cost to Helping, or is it only subject to the normal twist/condition rules that help is vulnerable to? Is help limited to things like Haggling and other skill tests (Dig for Leads, Use Facilities, Personal Business, etc.), or is the party able to do things like everyone helps with Circles and Resources?
You can definitely help with resources and circles. I’m not sure if helping puts you on the line for lifestyle, my guess is yes, but I’m not certain and don’t have chapter and verse.
Helping doesn’t cost you lifestyle but you are bound by the test resulsts.
Lifestyle costs are incurred by using services in town. See “Town Lifestyle” on p. 87: in general, you pay for making a test. Since helpers don’t make a test, they don’t have to pay. (This is the equivalent of using checks in camp; you don’t have to spend a check to help, only to make a test.)
As Jovialbard says, you can help with Resources and Circles (“Help”, p. 66). Beware of tax, though (see Praion’s point about results).
My quick-rule with torchbearer when I don’t have the book in front of me is to assume that the most brutal interpretation of the rule is probably the correct one 
The Rule of Ouch.
Helping in town is like helping in other parts of the game. You describe how you’re helping and hand over a die. You are subject to twists or conditions upon failure. Only the person rolling the dice increases their lifestyle obstacle. Players can help with Circles and Resources.
Thanks Thor!
On a failed Resources roll, does Tax apply to helpers?
Is it possible to help Circles or Resources with an appropriate Wise? (Thief’s Guild-Wise Perhaps, or Book-Wise if you’re buying a book, or even just Specific Town-Wise if you’re making a Circles/Resources test in that town.)