A Time & Materials contract is similar to being an hourly employee, at least in that you are paid a set rate for the actual hours that you worked, and you may be reimbursed for specific expenses such as hardware that you purchase for the company.

You don’t work, you don’t get paid (see my notes about unpaid holidays for more on this). If you are efficient, you might make less money overall, but if scope-creep enters in, you still get paid for all of your work. (Scope-creep is when you allow the defined set of boundaries for the work to be expanded.