Summary
Young brings most of his value on the defensive end, as he's a versatile defender who can guard multiple positions. Young has always been great at getting steals, finishing in the 79th percentile or better in steal rate for each season of his career (and 94th percentile or better each of the last 10 seasons), per Cleaning the Glass, and he does it without being someone that gambles a lot on defense.

Young is not as athletic as he was when he was younger, but he still moves pretty well and he's someone you can trust guarding out on the perimeter. He's also big enough to guard multiple positions.

Although he came into the league as a wing, he's transitioned to being more of a big at this stage of his career. He's even been playing some center in recent seasons. That might be his best position in today's NBA, as Young as never been a consistent three point shooter, so playing him at center allows teams to put four shooters around him. Young also has the playmaking skills to find teammates as the roll man, either in high-low situations or finding shooters.
 
Cap Considerations
Young will be an unrestricted free agent with a $21.3 million cap hold and full Bird rights. As his cap hold exceeds the salary he will get in free agency, and since the Raptors will be operating over the salary cap, his cap hold is not really relevant. 

Other teams will have multiple ways to sign Young as even teams without cap space could possibly use either the Non-Taxpayer MLE, Taxpayer MLE, or possibly even the Room MLE or Bi-Annual Exception to sign him.