If its a 2265 that looks and plays perfect its a great deal. If its a 2215 and looks and plays good it still ain't bad at all. I view any vintage receiver that works for $15 a good deal. Marantz are overrated IMO but people are willing to pay for the name so it is what it is. My personal preference is a Kenwood or Technics. They are cheaper and as long as they play will sound very much like that Marantz. I play an old Kenwood KA-4006 integrated amp about an hour per night along with an old Phillips 312 TT and Harman Kardon speakers from 1967. The sound is quite amazing. The whole setup cost me less than $150.
I have seen some marantz receivers go for 800 bucks used on ebay. I was suprised that it was 15. the technics was 25 but I couldn't get it to light up when plugging it in. the technics was about from the 70s also. even another customer said he was very suprised that it was 15. i knew he would have bought it if i didn't see it first.
Get some efficient speakers. That model puts out 38wpc. It's a late 70's model I think 77-79. Depending on condition they go anywhere from $50-$150. For $15 you did rather well. Personally Marantz during that era was on the downside. The Kenwoods and the Sansui's were beefier better built receivers at the time. Pop in an entry level TT and you should have a nice 2 channel rig. Don't have to worry about a phono they were standard back in the "OLD" days.
Those vintage Marantz receivers delivered significant power above their published specifications. Since Marantz built a wide range of pro amplifiers used by the most popular rock groups, and were designed using heavy duty components. Probably their best model from that time period was their 2600, rated @ 400W x 2 plus having a super 5 gang quartz-lock tuner and 3" scope for tuning and system applications. I have a close friend who sold a 2600 last year for $4500, and its original SRP was $1500..