DM_Fisk's Princes of the Apocalypse Campaign
Whenever the party is in a ‘safe’ location, they may elect to spend their downtime between adventures pursuing other activities. What the characters do is up to the players, and the amount of time they have between adventures is up to the group.
Ten days might be reasonable, or a month if someone needs to do some extensive travelling, or perhaps even just a single day… whatever the group agrees to do. However, be forewarned that the forces of evil will not be standing idly by while the adventurers take up pottery.
Always feel free to just describe what your character is doing during the downtime, there are many options for ideas, but if you have a different idea, feel free to pursue it.
You must pay the lifestyle cost for the time period, as described in the PHB, on pg 157. Certain abilities from character’s backgrounds or other sources might modify this this cost, as do many of the downtime options.
The downtime activities listed in the PHB (page 187) and the DMG (pages 127-131) are all available but may have additional rules.
Crafting – Create mundane items, including alchemical mixtures and herbal remedies.
Practice a Profession – Work and support yourself with your ‘non-adventuring’ skills.
Recuperate – Catch a nasty disease? Have some effect you can’t get rid of? This option MIGHT help.
Research – Work to gain insights into hidden mysteries, research magical secrets.
Training – spend time and money learning a new tool proficiency or language
Build a Stronghold – spend money and time to build your personal fortress.
Carouse – spend your free time boozing it up!
Craft a Magic item – A character can spend time crafting, or helping craft, magic items.
Gain Renown – spend your free time improving your relationship with various factions.
Perform Sacred Rites – spend your time in meditation and prayer. Seek guidance from higher powers.
Run a Business – Manage and run a business, instead of performing a profession.
Buy-Sell magic items – Rare items come from rare sources.
Sow Rumors – spread lies (or truths!) about your enemies to turn popular opinion against them.
Train to Gain levels – spend your time focused on your class abilities.