One possibility is to have the party be in the employ of a patron, granting them money or gear, boons and other rewards for their work. Such a patron can take many forms, from a merchant or a noble to a cleric of a temple, or a wizard, or the mayor of a town etc. Perhaps they are hired by a traveler as bodyguards.
Another is to give them their rewards one at a piece. Maybe one day they help out a hamlet and the fighter gets the masterwork armor the smith was working on in gratitude, another day they rescue a traveling sage and the wizards recieves a musty scroll, in a small town the rogue meets and cons an arrogant noble out of a tidy sum... you don't have to give every PC something every adventure, just make sure it evens out every few adventure.
Apart from this standard methods there are other methods. Maybe the PCs stumble upon the aftermath of a big battle between two groups and can loot the bodies.
Or the group is at the wrong time at the wrong place, gets mistaken for the contact of a thief, and gets a valuable "gift" - which leads to later adventures when the thieves come after them.
Or an important cleric/noble/cult leader had a vision, and now believes that the party has a great destiny in front of them, but fears that monetary concerns (greed) may deter them from the destined path - so his henchmen make sure that the heroes are always ready to take on the heroic quests, funneling them money in subtle ways (generous reward from a "wandering noble" for a simple task), convenient old adventurers looking for a fitting heir for their magic sword, a mage apprentice that only wants to write poetry and needs someone to dump that dusty spellbook on, and overconfident gambler... just plant the right amount of hints to make sure the players - if not the PCs - understand that this is not normal for your campaign. Soon the PCs will feel paranoid, when they always have a room at the inns they arrive at becaus someone is just leaving, or if they meet too many too friendly and helpful people, waiting for the other shoe to drop...