Should I get pre-approved for a loan before I speak to an agent?

[Mike Muniz]

Looking to invest in my first flip I have 50k to start. 15-20k for a down payment and 30k for a rehab,plus emergency funds. Do I have to get pre-approved for a loan before speaking to an agent about an offer?

For example.

Home is up for 100k and I want to make an offer say 75k. Do I try and get a loan off the asking price or do I wait to til the offer is accepted and then get the loan. Also if my loan includes the rehab ,do I make the offer and get the rehab estimates first or would I need to get pre-approved?