DM Academy

I have been DMing a campaign for the last few years that has downtime as an instrumental part of game play. Basically they run 2-3 adventures each month with the remainder of the 4 weeks of the month doing downtime activity. So I have some advice to make it fun and get the players involved.

First off I would look at the DMG, Xanathars Guide to Everything and Acquisition Inc source books because they all have rules for running downtime. That includes charging for lifestyle expenses and methods to make money. I would use those as the basis for what you are going to have the players do. The basics are do activity, risk money, make skill check(s) and get something back if pass or lose it if failure. What I do is just ask the players what they want to do and then debate / collaborate to getting this tied into one of the options. I wouldn't do it weekly as suggested in the book but rather a few times. That way the players can change their world this their two years and maybe make or lose (just as fun) money.

As for the ritual spells the wizard could realistically get all of those spells if they had the money (they likely don't) or the time (which they will). So I would use the spell scrolls costs to allow them to buy whatever scrolls they want and then copy it in the book. If realistically they can't buy the scrolls they might need to get charged extra to import it or spend time traveling to a larger city to buy them both of which will cost them extra. The amount of gold they have will limit what they can buy.

Just note that while its possible to get lots of lower level ritual spells with time the costs for higher level spells gets difficult to purchase. The wizard should be spending their money on spells and getting scrolls and spell books are fun for wizard players.

If you are worried about they using it make sure to track time in dungeons and other locations. It takes 10 minutes to cast these spells which eats into durations for other spells. I also make sure I account for time to move through a dungeon. I use 120 ft. (4x movement speed on average) for new territory for 10 minutes. They can move faster (10x) over terrain they have covered before since they aren't on the lookout for traps and monsters. I even roll for random monsters if appropriate in dungeons (typically 5-10% chance for one to appear) which forces people to take time into account. Its way more fun because they have to balance things. Do they want to keep their hour long spell up or waste their last 10 minutes casting Detect Magic as a ritual. These are fun decisions for a player to make.