My first PC was a Tandy 1000EX with 256K connected to a Commodore 1084S monitor.
You could add one proprietary card to it. To be able to add two cards, an expansion card could be added for $150. This also added 128k RAM to it as well. There were sockets for another 256k RAM for another $150.
Other fun cards I bought for the computer. These are specific to the 1000EX:
300kbps internal modem - $19. It was old and slow back then too.
Serial card - $100
1200kbps internal modem - $100
External 720k floppy drive - $149
Never bought a hard drive for it - they were external only and were $500+ for 40MB.
You could add one proprietary card to it. To be able to add two cards, an expansion card could be added for $150. This also added 128k RAM to it as well. There were sockets for another 256k RAM for another $150.
Other fun cards I bought for the computer. These are specific to the 1000EX:
300kbps internal modem - $19. It was old and slow back then too.
Serial card - $100
1200kbps internal modem - $100
External 720k floppy drive - $149
Never bought a hard drive for it - they were external only and were $500+ for 40MB.