Newbie,
Basically, you've just asked "how do I do rehabbing?" No offense meant, but you're not going to get the answers you need from a forum. Whole books/courses have been written on educating the investor on rehabbing. If you're not ready to purchase a book/course, then at least visit your local library and check out a few books on the subject. There is almost always one or two even in the poorly funded libraries.
As far as starting in rehabbing versus starting in wholesaling, there is no set level to start at in RE investing. If you want to be a rehabber, okay. A wholesaler, subject to investor, note buyer, etc., etc., then it's okay to start there. The real key is to learn the method that you want to do and learn it well.
Also, there are different levels of rehabbing, requiring different levels of knowledge/experience and $$$ invested. I wouldn't consider doing a major rehab for your first deal unless you really feel comfortable with your numbers and you have your contacts lined up to fix the place fast.
hope it helps,
Roger