The Italian is determined to improve his squad at the end of the season, but is hoping City can eventually be in a position to make only minimal changes on an annual basis.
"We are not like United," said Mancini. "They have a big history and we need a lot of years to compete with this.
"We need to improve our team every year and in the summer we need to buy the players who can make the difference, important players that can improve our team.
"We have our targets in the summer and we are already working on them.
"I don't know how much money we can spend but in the past United did spend a lot of money to buy important players. Now they don't need to spend £100million every year.
"United are a top team and they just need to buy one top player every year because they are strong.
"It is different for us. We need to do it this way and maybe in the next three or four years we need only buy one player in the summer because we have a strong team.
"It is impossible to say how much we will spend. We could find a player we need to spend only £1m on.
"We want to spend less money if possible but every time we go to buy one player the price is high. We try to spend less but we can't."