How much business can one conduct while in prison?

With the recent arrest of Aaron Hernandez, I was wondering how much business can one conduct while in jail (awaiting trial) or prison. For example:
*Last fall, Aaron formed a corporation that bought a $1.3m house. Assuming he is convicted, he won’t have much use for it so how can he sell it?
*How does he go about litigation with the New England Patriots now that they’ve terminated his contract and refuse to pay him money that is already earned?
*Assuming he’s got a few million bucks and he is convicted to serve a life sentence, can he keep the money and invest in stocks. There’s always a chance of parole in 20+ years. Can he access the money to buy supplies (e.g. cigarettes) or other party favors while in prison?
*Suppose someone owned a family business, could they run it from prison?
*How much contact are prisoners normally allowed with the outside world? Are they limited to a handful of phone calls per week and/or visits from outsiders?
*Can their “attorney” visit as often as they like and could the attorney carry out the business dealings of the prisoner?

In general, someone can grant the power of attorney to another person to manage their business affairs, including selling his house or managing his assets while he is in prison. With regards to frequency of phone calls and other conditions of imprisonment, plenty of details available from the Massachusetts Department of Corrections in their Family and Friends Handbook. (warning: pdf)

Hernandez has been charged with first degree murder and faces a mandatory sentence of life without parole. If convicted, he’ll never leave prison.

Speaking from my experience working in NY, you can pretty much buy as much as you want. The limits are:

*There are certain items you obviously can’t buy.
*There’s a maximum upper limit as to how much stuff you can fit in your cell. We don’t allow storage.
*You’re generally not allowed to buy things for other people or give your things away. (Although we’d usually look the other way for a certain reasonable amount.)
*You’re allowed to take two large bags plus a musical instrument plus your legal material when you transfer between prisons. Anything beyond that must be disposed of or shipped home at your expense.
*No item can have an official value of over fifty dollars. (Obviously, some items are worth more than fifty dollars. But officially that’s the maximum value.)