GURPS Traveller: Starports is the most detailed treatment. While there are a few GURPS specific rules in the character section, the Starport Design section can be readily used in Mongoose Traveller campaigns. Similar to how the economic rules in GURPS Traveller: Far Trader have worked their way into general use by the Traveller community.
You can download a Table of Contents here. Starport Design process in Chapter 5 takes you through all the steps of designing a starport. It starts out by estimating the trade volume in yearly d-tons of freight, passengers and revenue based on:
- Planet TL
- Planet population
- Port class vs expected class for that planet type (population and TL)
- Distance to nearest star system
The trade volume is used to calculate how much of each of the following resources the starport will need:
- Berths/Spacedock hangars
- Shuttle capacity
- Fuel processor
- Comercial space
- And much much more
Note the Starport Design process in Chapter 5 goes into budgets and personnel allocation at the end (page 86 to 87).
The books is a great resource for fleshing out a starport. It helps a GM put numbers to all sorts of variables on a starport. How many people are working in traffic control? How many ships arrive at the port each day and so forth.
However, it does not include a system for operating a starport. The income is fixed based on trade volume. Which again is based on things that a player wanting to run a starport has very little control over, planet population and technology level for instance. Neither does it take into account the amenities the starport has or hasn't. For instance having a casino adds no revenue or profit. Neither does a casino increased crime or draw tourists to your starport. It is just a line in the description same way as having a prayer room.