When to bring lenders in a deal?

[Amikad Kadogo]

Hi, I am very new to this and trying to get as much education as possible, so please forgive me if my question is stupid. I read in some books and posts that you need to secure a loan before making an offer so that you'd be ready to pay if your offer is accepted.

However, Brandon Turner in his webinars and videos encourages us to make as many offer as possible after working out the right numbers using the BP calculators. Knowing that offers will be rejected 90% of times, how would lenders like that if they approve your loan but you hardly use it? Is this strategy (make as many offers as you can based on the number that works for you using the BP calculator) for people who have all the money and don't need loans?