I have an opportunity to buy a TI 99/4A for a fair price. It does not include tape or disk drive. I can not find the edit/assemble cartridge on ebay so I am wondering what my options are if I want to play around with assembly on the TI-99 (cross compile or natively). The disk drives on ebay seem a bit expensive, would I be able to obtain an assembler on tape if I buy a tape drive and are there any solutions for transferring data from PC ?
I presume this purchase does not include the Peripheral Expansion Box (PEB). Besides the Editor/Assembler (E/A) cartridge, you need 32KiB expansion RAM and some means of storage such as the tape or disk storage you indicated. This would usually require a PEB populated with 32KiB and disk controller cards as well as one or more disk drives. You do not need a PEB for a tape drive, but disks are much easier to use. Fortunately, there are alternatives that are much more compact and cheaper. The periodically available nanoPEB (on EBay from seller Schmutzig1952) is an all-in-one solution that provides 32KiB expansion RAM, compact flash (CF) disk drive emulation and an RS232 serial port.
There are several alternatives for the E/A cartridge. The most attractive (and reasonably priced) is probably Ralph Benzinger's FlashROM99, which can store many, many cartridge binaries, including Fred Kaal's E/A II, in an onboard SD card.