You'd need two mobile radios, a controller, duplexer, power supply, feed line and antenna.
Trouble is, mobile radios don't make good high duty cycle transmitters. You'd need to turn the power down considerably to get them to not overheat, then the issue with them is some mobiles will become unstable if turned down to far.
You'll need a controller to work between the receiver radio and the transmitter radio. You may want it to send out periodic CW id (call sign). You want it to be able to shut the system down if it gets stuck in transmit mode. Most mobiles have a time out timer that can handle this.
Based on your location, you'd really want some way of being able to remotely shut it down. It's possible that someone can figure out your CTCSS or DCS squelch and cause issues.
Duplexer will be needed to combine the receiver and transmitter into one antenna. Trying to use separate antennas requires a lot of separation, more coax, additional antenna, etc.
Don't use "mobile" duplexers if you want this to work well. Use duplexers designed for the job. These may be expensive, but cutting corners here will result in poor performance. Get them professionally tuned for your frequency pair. This isn't something you can "eyeball" or guess at. It requires specific test equipment.
You'll need a good 12 volt power supply. Figure on battery backup if you want this to work when the power is out.
You need good coax. 1/2" heliax minimum, maybe bigger if your cable run is long.
Antennas. Without a good antenna all the money invested able will be wasted. You need a good antenna mounted up high and in the clear.
And, as they say, location, location, location. Without this repeater mounted in the right location, it's not going to do much good.
The repeater builder site is a good resource. Lots to be learned there. Just remember, don't cut corners if you want it to work well.
Icom mobiles are plentiful and cheap. Programming is easy. You can turn them down to low power (4 or 5 watts) and get some good life out of them. If you want more power, it would be a good idea to use a stand alone RF amplifier designed for repeater use. This will reduce strain on the transmitter and let the power amp put in the hard work.
Kenwoods are easy to find and programming software/cables are cheap.
Motorola is a good option. A couple of CDM-750's would be a good option, but programming software is expensive.
You could find a couple of older GM-300's and use those. Just make sure you get the lower power versions.
For the Motorola's, there is the RICK controller. There are some other interconnect cables you can find on e-Bay also.
For the Kenwood and Icom's there are different controllers available on line.
Adding a cooling fan to the transmitter can help a bit with longevity.
