Any character, including a henchman, is able to have structures built. Only PCs of name level can benefit from domain rules, however (e.g. tax, followers, monster-clearing, new settlements, etc.).

• Engineer-Architect: DMG 30.
• Construction Time: DMG 106.
• Construction Listing: DMG 107.
• Costs of Furnishings (as approximate reference): Dragon #117.

1. Player drafts a map (with grid scale) of the desired construction. The level of detail is up to the player. Some players like to make something simple and imagine the rest, whereas other players enjoy making detailed maps. Note that if a very simple map is presented and later on the details become relevant (e.g. if the building is besieged), the DM will have say on details not provided by the player.
2. Player uses the costs in the rules listing above in order to write up a proposal, which should include:
   1. List of prices for the construction and any furnishings.
   2. Required construction time.
   3. Calculated cost of architect-engineer (should include monthly cost of construction, plus one extra month for planning.)¹⁾)
   4. Total cost in money and time, and the total monthly upkeep cost.²⁾
3. Once DM approves proposal, DM provides player with timeline of the process (namely, dates which construction begins and ends).

Costs of building contents and furnishings do not need to be painfully considered. The player should just propose something that seems reasonable and not spend hours wondering if they've properly priced their dining chairs. Review the prices of items in the PHB and any other sources, and make a fair guess.