HHmmm, Well, you will have a few options. The legal way, (And if you plan to be a relay station between GMRS and Ham) would be to get two separate radios, one (preferably dual band) for ham, one for GMRS. If you go this route, I would say the TK880 low power (25W) would be a good start. With a power supply and proper wiring for RACES, you can make that radio swap from a vehicle to your house to a command post and will give you a legally dedicated part 95 radio for GMRS use. They typically go for about $60 on ebay. Youll need a programing cable ($10-20) and software (can be found for free) If you have a little more cash on hand the Motorola XPR4350 covers both 70CM HAM and GMRS bands at about $175. This radio is part 90, and will give you DMR options for the ham bands (if there is a local DMR repeater near you this would likely be a better option)
If you would like a lesser legal way, and I am not supporting this, though in an emergency it will work, is to get a reasonable ham radio (I used a yaesu 7900) and have a cap mod done which allows the radio to transmit out of band. This would give you both 2M and 70CM ham bands and access to the GMRS band though I would only run low power to prevent too much interference.
Next you'll need coax. If your only doing 20-30 feet, RG8x will be fine. Longer lengths and you may wish to find better coax. I used LMR200 for some time at about 60 feet and found it was reasonable, however that observation is irrelevant as your install situation will be different from mine. Being you'll likely eventually have several radios in the shack, you may wish to consider the LMR200 just to prevent inductance (I think thats the proper word, basically signal from one radio getting into the another radio through coax run very close to one another)
For antenna's, again, it will vary by install. A friend of mine runs a browning unidirectional antenna at about 20' up and has shown good results with low SWR. I have a couple antennas, One Tram hi-gain antenna for the repeater at 25-30' up and it gets about 6 miles range, and another being a diamond 200U which in the same install configuration only had 3 miles range. The use of the antenna also will change what type you will want to use. My understanding is that the higher gain antennas are more for repeater use, while lesser gain are better for mobiles and portables.
Im in no way an expert on this and am just going by the experience I had when starting out. Most of the comms stuff you learned in the past will cross over here. Use your best judgement, and if you have a question ask and you'll usually get an answer rather quickly.
