I was waiting on some one to say get a multi band! During my "google" search I ran across a guy who was recommending a multi band receiver if you can afford it, but once I saw the $1,200 price tag I almost choked!
Dave
First off let me say this....the worst built ham radio is still better than the best built CB radios, and that's no lie. So yes you have to pay to play. And ham radios aren't cheap.
Now as for your first radio....first find out what repeaters/frequencies are active in your area. IOW, if there's only 2 M repeaters, and no 70 CM repeaters, then invest in a 2 M radio. Vice versa if there's only 70 CM in your area. If both are active in your area, then yes get a dual bander. If 1.25 M is active then look into a tribander.
As for base vs. mobile, what most guys do is take a mobile radio, add a power supply, erect an antenna and call it a base.
Prices.....you can get a nice 2 M new for under $200. Look at the Yaesu FT 2900 (75 w.) or even the FT 2800 (65 w.) is good. They also have the FT 1900 which is a 55 w. rig.
70 CM only radios are harder to find and are more expensive. Kenwood had a few...TM 421 and TM 441 come to mind.
Dual band mobiles....I just did sell my Yaesu FT7900R this weekend, and I recommend this radio.
Here's another piece of advice....find out if there are any hamfests in your local area. A hamfest is basically a swap meet for ham gear. You can get some good deals there. Case in point, I bought a nice Kenwood TM 261A 2 M mobile radio there with mic and manual for $45....and just this weekend I bought an old Kenwood TR-7600 2 M mobile w/o the PL tone board (you'll want the tone board for non open repeater use, but it will work fine on open repeaters and/or simplex w/o it) for $15...with mic and bracket.
The multiband receivers are good for if you think you are going to ever upgrade to general, it gives you more radio to grow into. Yes they are costly but worth it. It also depends on what you want too. I have a Yaesu FT857 that I picked up for $700 used, and a Kenwood TS-2000 that I picked up for $1125 used.