Hi Damian
I have a 3.5 hp briggs same as yours on an edger and will take a few pics and post, the bend in the throttle linkage looks way excessive from memory. First things first though and that's to establish the non firing cause, usually no fuel, stale fuel, fuel restriction, no spark. You have seen the engine run so presume compression is present ? did he do anything out of the ordinary to start it ?
1. check that you have spark
2. If spark is good put a little fuel down the throat
3. pull start with throttle in run, it should at least fire, if it fires and then dies it will be a fuel issue
The choke does need to close fully in order for enough fuel to be drawn up to start, adjust the cable so it fully closes the butterfly. Drain the fuel if your not sure of it's quality and put some fresh in and try to start. If it won't start after a couple of pulls you most likely have a fuel starvation issue which is normally only caused by a couple of things.
Has the mower been sitting for a period since you bought it?
Cheers
wce
