@Leandro Rodriguez
When I started in RE investing I was going to approach an acquaintance that has several hundred units and see if he would be willing to mentor. However, I decided that I should first do some basic research so I wasn't just asking basic/obvious questions. I came across BP as part of that research and rest is history!
I started out listening to the podcasts to get a broad overview of the RE field - wholesaling, SFR, MFR, etc. I then got into reading specific forum posts and blogs along with some of the books posted here. I started thinking about investing as a business, and started organizing the parts I needed to make that business successful.
After a few false starts (mostly being too conservative when bidding) I ended up with a few properties. Now whenever I have an issue my first stop is to do basic research on BP or post a question to get fellow BP'r feedback. It has been fantastic - instead of one mentor I feel like I have 1000 mentors all ready to help out.
So while this is not an answer on how to vet a specific mentor I just wanted to tell how I feel BP is a community of mentors that you can rely on to get started, give advice, help vet deals and point you to any number of resources you need to be successful!