I THINK what Sensible will be referring to is the common rental policies of the majority of FBO's out here.
As he says, C172 and PA28 are available by the hundred. Getting anything bigger than a four seater can be "difficult" at best - even in the single engine variety.
Getting a twin to self fly, even a common one such as Seneca/Seminole/Duchess often requires a good, long standing, reputation with the FBO, 500 hours MEP time, 100 on make/model - all sorts of nightmares.
Some operators have even taken the middle row of seats out of the Seneca and made it into a four seat aircraft.
Getting hold of a PA31 to fly solo, I would expect to be "a dream", getting hold of one to take away for two weeks and only do two hours a day is moving towards a fantasy.
It will, of course, all depend on your MEP experience - and remember that, at least in JAA land, time on a 744 does not count as experience towards an MEP.
I truly wish you the best of luck - if you find one let me know - I've been trying to get hold of one (even for a "one hour local") for over seven years now.....and that's with 1,000 command on type.