The think to bear in mind is that its not investment in any case, its a donation.
John Wilkinson made a long series of heavy donations to Salford over 20 years - £millions. The "return" on that "investment" was the impending closure of the club with major debts and what few assets they had left being stripped.
Equally "investment" went into Oldham in their Superleague days. AFAIK their asset of Watersheddings was sold to pay back the investor some of the millions wasted and the club financially collapsed and ended up playing small new clubs in a third tier.
Great point JohnM. Where someone is happy to "donate" clubs can get away with just taking the money but when the donations stop collapse is usually the result.
Where someone "invests" and want's a return on that money, or at least to be paid back, a club can be destroyed by this.
Putting millions into a small club is a wonderful ride until they hit the buffers then collapse and destruction results. The game has to live within it's means so P & R far from being a great way of attracting money for nothing (short term) is a great way of destroying clubs out of their depth long term.