xEM Compatibility with Schlage IBF-120?

Are you certain your apartment complex uses both frequencies?
It would be uncommon, but not impossible.

If it only used the Low Frequency, then the Blue cloner would be fine, as it does HID reading / writing

DT no longer sell them, but you can find one in many “usual” online shopping places.
Amazon, ebay, Aliexpress etc…

Just make sure it specifies HID, there are a lot that look the same, but what lies beneath the surface may be different.

It should work fine writing to a Fob, but to an implant you may want to do a simple modification