Amazingly, my first job after graduation from UCSD in 1992 was doing tech support for Quick Link II Fax, which is the software that came with pretty much all fax/modems in the 90's. I eventually went on to write the User's Guide for this terrible software, both for DOS (which used TSR's to fax from any printing software) and for Windows 3.1.
Anyway, fax/modems are still out there, but they are terribly annoying in many ways. They made sense when a real fax machine was $500 and a fax/modem was just $100 and you were going to buy a modem anyway to get online to your BBS or CompuServe, but not anymore.
To receive a fax with a fax modem, your computer must always be turned on (and not asleep) and the fax software must always be running in the background. It is very helpful for the fax modem to have a dedicated phone line. To send a fax, you either need to print to a fax driver in windows (but then you might as well just print to a PDF maker in windows and send an email), or scan something with a scanner and then send it out. Very annoying.
Better options:
1. Get a printer/scanner/fax device. My favorite is the Epson Artisan 800, even though it drinks ink like it was water. It prints, scans, copies, faxes, prints on CDs, and supports wired ethernet and wireless network printing. You'll probably still want a dedicated phone line for lots of faxing.
2. Efax or similar internet faxing service. You'd still need to scan handwritten things to fax, but at least you don't need a phone line for it.
3. Buy a cheap fax machine. Office Depot has one or two models under $70.
-Llama