The 32-year-old left the 'Villains' this summer after 14 years with the club, in which he made 391 appearances and scored 86 goals.
Former England international Agbonlahor says he was ready to help the club as they faced financial problems ahead of a summer takeover.
Villa had failed to gain promotion last summer after losing to Fulham in a play-off final, whereafter Agbonlahor proposed the idea.
He remarked: "I was aware a couple of strikers had what seemed to be long-term injuries and everyone knew the club had financial difficulties, so I asked my agent to speak with Steve Bruce and make the offer I would play for free.
"There were no strings attached, I didn't want paying, no appearance money, nothing, it was a genuine offer to help the club I love.
"The manager had been good for me when he arrived. I had been in a bad place before he was appointed and he gave me the opportunity to get back involved.
"He was appreciative of my offer but no one was aware the club was in the final stages of being sold to sort the financial problems."
Despite now having departed Villa Park, Agbonlahor does not want to retire just yet: "It's been a difficult decision. Having been at Villa all my career, I did not want to play for another Championship club.
"I appreciate the offers, it just didn't feel right. As for the SPL, unless it's one of the big couple of clubs, to be honest, that doesn't excite me.
"There has been interest from the Middle East, Turkey and Thailand and that new challenge, lifestyle and opportunity interests me but I have a young family and I'm very conscious of the impact playing abroad would have.
"I don't need to chase a deal and will only sign for a club that genuinely excites me. I have no interest playing below Championship level so abroad realistically is the likely destination if I decide to make that decision.
"I am fortunate I've had the same agent, Tim Webb, all of my career and he has been great looking after all of my finances and investments, so financially there is no need to accept anything that doesn't really work for me and my family.
"I don't want to retire yet. I admit I have made some mistakes, I do have some regrets but that's life, who hasn't made mistakes? Hopefully I will be remembered by the [Aston Villa] fans for the good times."