Apothecary

Apothecaries sell medicine and potions.

Downtime Activity: Training
You can spend time with an instructor here to gain proficiency with alchemist's supplies, brewer's supplies, cook's utensils, an herbalism kit, or a poisoner's kit.

Resources. Receiving training in a language or tool typically takes at least ten workweeks (50 days), but this time is reduced by a number of workweeks equal to your Intelligence modifier. A negative Intelligence modifier doesn't increase the time required for training. In addition you need to find a teacher and pay 25 gp per workweek.

Resolution. At the end of your training, gain that new proficiency.

Downtime Activity: Crafting
If you are proficient with an herbalism kit and you're on good terms with the proprietor of this establishment, you can use the facilities here to create potions.

Resources. Crafting an item requires raw materials. And an amount of downtime. At the DM's discretion, some potions my require rare materials that will need to be collected from exotic locations and monsters. Collecting these materials may reduce the total cost of creating the potion.

Multiple characters can combine their efforts. Divide the time needed to create an item by the number of players working on it. A particularly tiny item, like a ring, might only allow one or two workers at a time, whereas a larger, more complex item might allow for four or more workers. A character must be proficient with the proper tools to craft an item and must have access to proper equipment.

Resolution. Once the proper materials are collected and the proper time has been spent, you successfully craft the item. You can sell the crafted item at its listed price if you so desire.

Brewing Potions of Healing. Potions of healing fall into a special category for item crafting. You still need to be proficient with the herbalist kit to create these potions, but the crafting time and material cost are different than other potions.