We will be following a point buy system.
For this game, I'm gonna go with a 28 point buy
for your abilities, before bonus points from leveling and from race. Starting with Pathfinder standard (everything starts at 10, which is free and costs 0 points).
Here is a point buy calculator: http://tools.digitalightbulb.com/pbcalc.html
Since scores below 10 actually add more points for you to buy other scores with, I'm okay with you reducing your score below 7, and I'll just do special math for that. Bear in mind that a score below 7 is a big weakness, but it will allow you to have a lot of strength in other places. Each step below 7 will add another -1.
It will look like this:
6 = -5
5 = -6
4 = -7
3 = -8
You could have, through this, three 18's as your scores. However, you would also have two 3's and a 4, so you would dominate in some things and struggle in others.
Also, I'd like everyone to start their characters at level 8.