Aestilon

During downtime, the players can invest some time in various activities. Players can work on their immediate future, or start preparing for a furtherfuture. You can set things in motion for later in the campaign.

See: https://roll20.net/compendium/dnd5e/Expenses#content

Practicing a profession allows you to live a modest lifestyle without paying the cost as long as you keep working. If you are apart of a guild or group, like a thieves guild, you instead gain enough for a comfortable lifestyle. Finally, if your character is willing to put themselves out there and has a proficiency in performance, they can perform and maintain a wealthy lifestyle without paying the cost.

If you choose to live a lower lifestyle, you can keep the difference as income.

To be filled with better rules than 5e base, but you can essentially invest time in crafting, including the crafting of magical weapons. Obviously, as adventurers yourself, crafting isn't a thing you spend time on yourself, you will enlist professional craftsmen to do so.