Income upgrades
The Roblox description explicitly says you can upgrade your income. Open the current upgrade interface and compare its displayed cost and result before purchasing.
Other upgrades
The description also says “your upgrades” can be upgraded, but it does not list categories or effects. Use the labels and tooltips in the live game; this guide does not assign undocumented bonuses.
Spend with current values
Prices and balancing can change. Compare the displayed cost with your current Cash and note the result after one purchase before planning a longer upgrade path.
The game facts on this page are based on the official Roblox experience listing.