If you want to reach lvl 100 in the fastest way possible than this guide is for you! the trick uses the patch #5 update to its advantage. Rats overkill pro job gives an incredible amount of xp and can be completed very quickly.

Day 1
On day 1 all you have to do is run into the house and go into the bathroom, in the bathroom you usually find atleast 2 ingredients and thats all you need because you are supposed to blow up the lab. if there is 2+ players then 1 player runs to the house and the other 3 wait in the car

Day 2
On day 2 you look around and try to find the place where a gangster is standing infront of a door/entrance. Thats usually where the safe is. Once you find the safe i reccomend either blowing it up or lock picking since its much quicker than drilling.

Day 3
This is where you get the cash, all you need to do is kill al the gangsters and then open 4 suitcases(if 4 otherwise open an equivalent amount to the players) and take 4 bags all at once(ignore the C4). Then you just escape while holding 1 bag each and you get your payment :D
sometimes there spawns a money bag and coke near the escape and coke is worth more than money so i reccomend 1 of the players takes the coke

You should not get any bags of meth if you want to level as fast as possible since the extra time it takes is not worth it
You might want to take all money bags in the bus if you can since the cash will be much greater but if you just want XP then taking the least amount of bags is best