That's what I'm talking about! I'd like to keep the antenna at 10 feet or less and I'll use fence top rail for a mast to clear the roofline. I'd like to get a quality antenna that I can tune, then tune back after we get our licenses. Any recommendations? Also, if I drive the fence top rail 4 feet in the ground, would I need a separate ground rod? I'm sure it's not up to code in some areas, but I don't want to start tying into her electric boxes or mess with her ground rod. I have enough issues with her without being blamed for blowing her electric service I would use a lightning arrester.
Grounding rods are typically 6 feet deep and copper. For proper protection, you would want to ground the mast and the cable at the mast side, and as close to the radio as possible, with the ground wire being as short as possible. Use clamps for everything; don't solder. Lightning will melt solder joints. During times of the year when lightning occurs in any given operating area, most people disconnect the cables when the radio is not in service. Proper grounding still doesn't fully arrest direct or near-direct strikes.
As far as antennas go, if you are looking at 2m/70cm/GMRS specifically, I have a Diamond X50a on my house. It has a 1.8:1 SWR on 462 MHz and a 1.6:1 SWR in 467 MHz. Those are your baseline frequencies for GMRS simplex and repeaters (respectively). Those are about $100 each.
There is another Diamond that could work... but I have zero experience with it and I don't know anyone who has used one. Keep in mind, multipurpose tools like an all-bander antenna will work, but there will be a compromise on performance compared to dedicated antennas. That said, there is a Diamond Super Discone (like the D130J) that are somewhat of an all-bander antenna, for about $100 each. For the D130J, specifically, on VHF and UHF its rated for 200 watts. Below 144MHz, its only rated for 20 watts on FM and 50 watts on SSB.
You would want to either buy or borrow and antenna analyzer to dial it in. Also, order some quality coax cable.