Several points here:
1) United's problem is currently that people lend a shedload of money to buy them. A consortium of 6 people won't be playing with their own cash.
2) Nobody is going to buy United. There's no money in it. United have saturated every possible market, have massive sponsorship deals and have some of the highest ticket prices in the league, there's no potential for growth, their fanbase is already as big as it's going to get. You'd have to put £200m in to the squad too, to get them winning leagues and CLs again after the older players have gone, as their youth just isn't good enough to cut it. So, you're going to spend £1.2bn, to earn what? £50m net per year? (presuming they win the league and CL every year). By that rate, it will take 25 years to show any sort of profit. This also doesn't take in to account the boom and bust nature of football. Just like the Italian and Spanish leagues, the Premiership's revenues will eventually drop, which means United's revenue will drop significantly.
Any businessman worth their salt, would buy a club who already has a big, new ground, plough a couple of hundred million into it and turn a profit in 5 years.
United are too big, and too oversaturated to buy for £1bn. They're probably worth half that.