The maximum attainable level

As far as I know, there are no prerequisites for pro jobs (I saw them from the lowest reputation levels). The difference in comparison to normal jobs is that you cannot try the mission again if you fail. You get one try and that's it.

Another thing that makes pro jobs special is that there are no pro jobs on normal difficulty. They are always on hard, very hard or overkill.

When you first start PD2 you will have a penalty depending on the heist type compared to your level.

There is a table on this link which shows different values for heists based on level: http://payday.wikia.com/wiki/Reputation_(Payday_2)

Any XP / cash rewards are only for you. You and your crew will have different modifers such as Infamy bonus, XP repeat heist penalty, XP level penalty, bonus XP from perk deck, etc. Which was one of the reasons I stopped getting Dead Presidents, as it didn't benefit the crew.

You can avoid the XP reduction for repeating heists penalty by not repeating the same missions over and over, spread them out over lots of different missions. Once you get this negative modifier it takes a while to get rid of it. But if you do a Stealh job that can offset some of the lost XP.

Sources: http://payday.wikia.com/wiki/Reputation_(Payday_2)

And nearly 1,000 hours gametime!