Listings are asking for pre-approval letter

[Renee' Dixon]

I'm a new investor. I keep seeing the articles that say "make multiple offers" &  "just  get out there" to get started but it seems like all of the listings that I see these days, the realtor is asking for a pre-approval letter.  I have no funds & I'm not in a position to get a bank loan just yet so what do I do?