If you go the used gun route then check CT to make sure they make a laser grip that will work with that grip frame. Used S&W revolvers can be had at reasonable prices if one looks around for one. The kicker is that most times the laser grip cost half of what the gun did. Sometimes almost as much as the gun did. Buying new the price with the laser grip on it price tends to be about $50 to $85 cheaper than buying both separately.
No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.