Hi Kate and welcome to our friendly little forum!
I'm impressed that you've saved to take time out for making music. I personally take the other approach (to be distracted and poor) but I'd like to do what you do!
As for Yamaha or Korg, I'm not the man to answer that question. Have a nose through the recording forum, and post your question; I'm sure you'll get some great advice from our members.
Looking forward to hearing your music.
Tone