The place where Decimus lives with family is outside of Rome. But for the business he has inside the city he lives in an minor house with poor decoration which doesn't really scream out wealth and prosper.
His wealth at 84 BC
Spoiler Alert, click show to read: 

Starting wealth: 7,500
Base income:
Trade:
Salary: 5000
Farms: 1,000
Mining:
Other:
Sum:13,500

minus

Expenditures
Upkeep:
Slaves: 8,000 ( 40 slaves )
Cavalry:
Missile:
Legions:
Liburna:
Small Farms: 1,000
Large Farms:
Latifundia:
Mining venture:
Other:
Sum:
Starting wealth next year: 4,500