Here’s a thread from two years ago. Some of the technology used then may be a little out dated, but the timelines, tips and general information are still useful. Some people choose to pay someone to do their videos, but doing the video on an iPhone is perfectly adequate. In order to get a good sound balance you might prerecord the piano accompaniment so you can adjust the volume and the piano doesn’t overpower the singer - very common in recordings with “live” accompanist.