As you work with MJ during his "Herbalism" side mission, you will increase up your Herbalism level each time you hit a specific monetary goal. Each time you level up, you will unlock a handful of upgrades for the Grow House, ranging from better lighting that improves the growth rate of your herbs to enhanced air conditioning units that improve the quality of your product.
There are seventeen upgrades worth purchasing in total. The first tier of upgrades for every category will already be available for purchase when you begin your operations; however, there are several that will only become available as you level up your Herbalism level. Please refer below for all of the upgrades that can be unlocked/purchased at the Workbench in the Grow House.
Planters
Level 1 - $4,000
Level 2 - $7,000 (required level: 2)
Level 3 - $11,000 (required level: 3)
Level 4 - $15,000 (required level: 4)
Level 5 - $20,000 (required level: MAX)
Lighting
Level 1 - $5,000 (required level: 3)
Level 2 - $10,000 (required level: 4)
Water
Level 1 - $4,000 (required level: 3)
Level 2 - $7,000 (required level: 4)
Air Conditioning
Level 1 - $2,500 (required level: 3)
Level 2 - $4,500 (required level: 4)
Fertilizer
Level 1 - $10,000 (required level: 3)
Once you have purchased the final upgrade for the Grow House, the achievement will unlock.