Hey sarah, I say go for it. Just the other day after watching Tammy's slideshow a million times over again and again, I went ahead and got a program to do slideshows. Then I started thinking I would do it on the side to pay for the software.
If it's somethign that you LOVE doing then absolutley go for it! As for price I was thinking it would depend on how many hours you put into each slideshow, depending on the client.
Good luck!