I would do both. For promotional content just hire someone and do 4 or 5 songs (different genres/styles). You don't really have to do the whole 3-5 minutes for each song. Just do a short version of each song to prove a point. You can pre-record the audio part ahead of time. If you prepare the content properly, it will reduce the cost significantly.

Then, I would also open a YouTube channel, and record my own stuff whenever.

If you're doing your own original songs, you don't have to worry about copyright problems on YouTube.