If he was selling an AR, would you come in here and say, "hey, fellas. What's an AR-15 worth? I think it was made in the 90s and has a little rust." Like amy other rifle, mini 14s can vary a lot in price. You have to know what you hav first, and then go from there.
Look at the prefix for the serial number. If it starts with 180 it will be tough to sell to anyone unless they're a collector or have no idea what they're looking at. Parts are no longer made, stocks aren't necessarily compatible and even Ruger has basically disavowed it.
They went until 2004 or so and ended in the 197-ish serial numbers. That's when they started with the 580 prefix, and went up from there. The newer rifles are generally better, especially those with the flared barrels (as opposed to the older "pencil barrels" that were phased out around that time).
The original 181+ rifles had pretty decent iron sights but mounting a scope was an exercise in rube goldberg gunsmithing. The 197 Ranch Rifles were set up for scopes, but have abysmal folding "backup sights." The newer rifles have nice peep sights. There are tactical versions with shorter barrels, etc.
Then you have the older GB series, with the bayonet lugs, that are sought after and have a bit more value than the others.
If the mags are truly Ruger brand 30 rounders, (especially "pre ban") those may hold significant value - especially to anyone in a ban state.
I love mini 14s, but I got mine (a 197 Ranch) when they were around $350 and an AR was pushing $1000. As much as i love them, even I have to admit they are overpriced right now. Now is the time to sell. Get some more specifics about what rifle it is and you'll get a better answer.