Lasers are for speed and movement that result in sub-optimal firing positions or lighting conditions. Not for precision. This holding a laser on someone is hollywood balony that is going to get someone killed.
They can be used for precision training as a dry-fire aid. But don't use these to shoot groups.
There are no good cheap lasers. The cheap ones are essentially AirSoft / Paintball Geegaws. They function, as in they throw a beam. But they won't hold their zero, or likely live if they are subjected to use on a real firearm. Typically anything that is a "universal fit" laser is going to be a toy grade piece of junk. It will also immediately limit your holster options. IMO Crimson Trace laser grips are the ONLY way to go.
Crimson Trace and LaserLyte are about the only dedicated lasers I would trust. Surefire and Streamlight also have good lasers as part of their flashlights. You are looking at about $200 on average to get into lasers aftermarket. It's a little cheaper if you buy the laser grips already on the gun, but you say this guy is on a budget so a $500 gun with an extra $150 of laser grips bundled into the price is probably going to put most folks on a budget looking for alternatives.
Keep in mind that you need to tell your friend to stick with popular handguns so that there are actually laser grips made for it. No Taurus, Ruger 9E, Arcus 98, Ruger P90, etc, etc because it was cheap. You won't find quality laser grips for those guns.
My advice for a budget........Look around for a Police Department Trade-In Glock 23. Then scour eBay, gunbroker, and message boards looking for a set of lightly used Crimson Trace laser grips. Do your part, and you can probably get away for less than $500 for the TOTAL investment of gun, transfer, taxes, and the laser grips. You may do even better and get the whole set up for under $400 if you are lucky.