I'm working on a short-term marketing project that will only last about two months. I need a dedicated phone line for people to call in and leave their contact info. I don't want to sign a long contract with a big provider for such a short period. Is there an option to just pay for a month or two? How fast can I get a number up and running?

For short-term stuff like that, you definitely shouldn't go to a traditional carrier because they'll try to lock you into a 12-month deal. Your best bet is to rent a phone number through a service like DID Virtual Numbers https://didvirtualnumbers.com/en/ You can get a number active in literally a few minutes after signing up.
I used them for a summer pop-up shop last year and it was incredibly convenient. You just pay for the time you need and then let it expire when the project is over. You can even set up an automated answering machine so people can leave their details without you being on the phone 24/7.
It’s very flexible and you can manage the whole thing from your laptop. I found the pricing to be the most competitive for these kinds of temporary needs. It saves a lot of hassle with paperwork and credit checks.

The automated answering machine idea is a total game changer for my workflow. It's exactly what I need to handle the influx of calls without hiring an assistant. Thanks for the suggestion, it sounds like the perfect fit for my budget.