Aston Villa fans want to know where the club's projected summer transfer budget of £20 million has come from.
Villa chairman Doug Ellis has given the go-ahead for O'Leary to bring in four top quality players to bolster one of the smallest clubs in the Barclays Premiership.
It is a U-turn by Ellis after previously indicating there was only around £4 million in the kitty for O'Leary, who had been looking to bring in bargain basement signings.
And it comes after hopes of selling off land near Villa Park for £20-25 million had been scuppered by a failure to obtain planning permission.
Villa Fans Combined (VFC) spokesman Jonathan Fear said: "I think fans share David O'Leary's shock at the news that the club may actually be backing him to the tune of £20 million.
"We also share his comments that the club, the squad and the fans need some good news.
"We have heard this sort of talk before though so we hope this time to actually see it happen, we have had false promises and unrealistic targets for far too long. We now need action not words.
"I can see no way back for Mr Ellis if he doesn't now deliver on the promises made. It would have a very negative impact on the club and would be the final straw.
"It would be very interesting to know where the funds are coming from especially following the collapse of the planning permission for the land Villa own in Aston which has prevented their sales.
"I would hope this doesn't mean the much- needed improvements at Bodymoor Heath are going to be shelved.
"The main worry is if the redevelopment - which will apparently cost in the region of £8 milion - and the squad rebuilding are going to be funded by loans when the board have been unable to generate profits over the past four or five years.
"However without seeing the full details it is very hard for the fans to fully evaluate what exactly is going on at Villa."
Fear admitted: "Like all Villa fans, we are just hoping to see our team being restored to the position where they can compete not only in the Premiership but also in Europe.
"For David O'Leary to be judged he needs to be backed. One thing is for certain, it is a very necessary investment and, if the promises are fulfilled, the fans that are at the moment considering whether to renew season tickets next season may well be swayed.
"It may also stop players from feeling they are going nowhere at this club and mean they are more happy to stay and fight for their shirts.
"As the manager says, it is then crucial that this investment is topped up each summer so that we don't fall back into the wasted seasons of stagnating."