Used G2 or G3 Glock, used S&W M&P series or maybe a new RIA 1911.
Don't be scared by RIA 1911s for their price. They're the only 1911 I'll buy and I have yet to have a complaint about one.
Agree with RIA 1911 in .45 as good option. Picked mine up for $450
What he said.
Both the Ruger and the RIA 1911 pattern are pretty dependable plain jane pistols. I have had both pass through my hands with no problems. Good Luck
Several options out there, he can get new RI or ATI 1911's for under $500. A Glock, S&W M&P, or a Springfield Armory XD will run you at or just over $500. Depends on the style of 45ACP he wants.