Certainly a twin, and certainly 5 passengers.
Restrictions are 5.7 tonnes, 6 seats, 250kt cruise, 14,000ft.
So rules out pressurised TPs and jets (for all practical purposes), but not much else.
And why not? The purpose of regulation should be the protection of innocent third parties. In commercial air transport this means primarily the passengers, there are many of them and if things go badly wrong, they all die.
In private, small aircraft flying this means poor sods on the ground who are hit by crashing aircraft, which is extremely rare, and very few passengers who are flying for leisure or personal transport with a friend or relative, who hopefully know better than to get in the aircraft with the wheezing diabetic just recovered from triple bypass surgery, even if the pilot clearly has no safe-preservation instincts at all.