Having done this I can comment on it.
First you don't need an industrial sewing machine unless you plan on doing years of sewing for many hours per year. A $100 - $500 machine will be perfectly serviceable. I have had three machines, spent $100 on the first two and got the third on sale for $250. (ex wives took the first two in divorce)
http://www.amazon.com/Janome-HD1000...=8-3&keywords=sewing+machines+janomeDon't get a fancy electronic machine, just the basic stitches is fine.
Doing it to save money on just one project won't work out because it will take you a few projects to get good at it. If you plan on doing several projects then yes over the long term you will save money, BUT your time will be in trade for those savings. If you are a person that makes decent money working, the don't bother, work some extra OT and pony up the dough and save yourself the headaches.
Unless you take a lot of pride in learning a new skill and enjoy using things you made with your own hands.
One of the benefits of DIY is custom work, you can make the clothing fit YOU and put little extra features in your tent or tarp that the manufacturer wont.
Be willing to take the time to learn and get good at it, this means starting off with easy projects and working your way up. Stuff sacks and meat bags are easy to do and a good way to start, then basic flat tarps. Then clothing, like a vest, then a jacket.
The biggest time saver/sink is having big table space. You need to build or cobble together one big enough to handle bolts of material. At least 6 feet wide and 6 feet long or longer, longer is better. Doing this will save you a lot of time and decreases the odds of making a mistake.
Also have plenty of light for your cutting table.
Have fun.