Nothing wrong with MrBeer kits as a starting point. In fact, you may not want to brew 5g batches. I'm set up to do 10g batches but only brew 2.5g batches cuz I can't drink it fast enough before it starts heading south. The plastic bottles in the MB kits are just fine.. but, they are large.. and I need someone to help me drink that much at one sitting.
If MrB is the way you want to go.. first check Craigslist.. I see them on there every so often. but beware of the price.. I wouldn't spend more than $10 for one on CL. Here is what I'd do if no luck on CL. Go to the MB website and order one or two KEGS only.. they are only $10 each. Then you can order whatever extract kits you like. Have friends save their NON SCREWCAP bottles for you. Heck, you can even bottle your beer in personal soda bottles or "craft" water bottles like arrowhead, etc. (not the kind with the drinking cap.. just the regular screw cap). Just keep those clear bottles out of the light while you are storing them. Otherwise, go to you homebrew shop and buy about 24 bottles w/caps and a capper of your choice. There are inexpensive "wing" cappers as well as the desktop kind that work like a charm.