Hi Guys!
I'm considering picking up a Yamaha SG 30 build in 1974.
Does anyone of you have some information about that guitar? Is it any good? Could find next to nothing on the internet.

Thanks on advance!
It depends on how much you are buying it for. The SG is a pretty decent to amazing guitar depending on which level you are getting. I wouldn't buy anything less than a 500. For the prices that I have seen some of the lower model numbers go for I would rather save a couple more hundred and get a 500 or greater. Ideally a 1000 or 2000, those guitars are on my GAS list.
Gibson LP traditional and DC standard, SG standard, MIA Standard Strat, Schecter Banshee 7(*for sale*)
EVH 5153, Orange TV50H 2-2x12's
Line 6 M13
The SG30, 35, 55 etc are an earlier variation on the SG range so the numbers are not directly related to the 500/1000/2000 etc. but I think the SG30 is still the most basic "no frills" version of that particular iteration of the SG model. Probably an excellent guitar, as most Yamahas from that period were. But not something you should expect to pay any sort of vintage premium for.
Live Rig January 2018

Fender Baja Telecaster/Danelectro DC-12
Boss TU-3, Ibanez TS9, Fulltone OCD 1.7, Boss CS-3, EHX Small Clone, MXR Carbon Copy
1964 Vox AC30TB with '69 Rola G12M "blackbacks"
Elixir Nanoweb 10-52 strings, Dunlop Jazz III XL picks
^^^ Good point. Don't be allowing the word "vintage" to come into any conversation that has anything to do with price on those guitars. They weren't particularly popular.

You'll want to be pretty objective in comparing them to, say, current Korean, Chinese or Indonesian guitars.
Not looking for any hidden gem in this guitar. I'm searching for a cheap, solid and decent guitar which can take some hits on stage. He wants 375$ for it. But he's open to go down. Is it worth it?