Whats the price, a saiga is strong and built proper, future conversion if thats an issue will cost a little, saigas stock are pretty bare, factory hunting stock, no muzzle break, etc, The only thing i can think of you should check out is the rifling make sure the barrel isnt scratched do to improper cleaning, your not going to have canting, rivit issues on a saiga.
Also there are hundreds of post askin your very same question, I would type saiga into the search box and there you will find many answers to your saiga questions.
Ammo and mags are still easy to find. AKfiles.com, AR15.com classifieds. The price has just gone up on em. Mags are $20-30+ and ammo is ~$160 for a 1080 spam can. I found picked up 2 cans at the last gun show for $140 each.. Its still out there.