This is essentially electroplating. Electroplating isn't hard to do, at least on the home experimentation level.
I have occasionally made my own electroplating setup at home. Just using a variable, regulated power supply, some wire and an old, plastic margarine container filled with a weak solution of muriatic acid you can easily electroplate the copper off a penny and deposit it onto a quarter. I once caught a wild hare and got the idea to plate copper onto my house key so it would be a different color than the others.
I did everything myself and determined what I needed to know empirically. I built my own regulated power supply with parts from Radio Shack. Schematics from the internet. I made the apparatus and got it working. To determine how much voltage/current to use, I adjusted the power supply until I could just barely see bubbles coming off the electrode then backed down a bit from there. I let it run over night. In the morning, I had a copper plated house key.
Silver recovery, although a little different, uses the same principles. Instead of making your own power supply, you could probably use the wall wart transformer from an old cell phone charger that you don't use anymore. It doesn't necessarily have to be regulated. Many wall warts are already regulated, however. It shouldn't be a problem if, instead of an adjustable power supply, you put a potentiometer in line. It's not the preferred way but it will still work. So what if you overload the transformer? You recycled it from being tossed in the garbage, anyway. Right? For the plating electrode, I would probably use a silver coin. If you could find silver foil, more's the better.
I see no reason why an enterprising person couldn't take what I just wrote and figure it out for himself.
I have done projects like this in the past and I will likely do similar projects in the future. I'm a natural tinkerer. These are things I like to do for fun.
I could probably create a project like this for $50, more or less, using materials from around the house.
I just felt that the time I would have spent building, testing and experimenting would be better served making photographs in the darkroom instead of tinkering in the garage. To each, his own. Decide on your personal circumstances and inclination.
In the end, I agree with John. It doesn't matter how you do it. Just do it.
You'll be doing a good thing for the environment. You'll be dumping money down the drain if you don't.