I personally don’t think it has any effect. An author under the same of StockSounds has been a member since January 2013, and appeared mostly dormant until around April 2015 when he started regularly releasing tracks. He is now a top selling author making 800-900 sales per month. I’m sure there are plenty of other authors who began their accounts as buyers and years later became sellers. Just ask @stardiva, who has been a member for over 7 years but only recently started selling in late 2014! I believe TimMcMorris was also initially a buyer until he started selling here about a year after he joined.
I created an account in December 2014 but started selling in April 2015. I initially thought this could put me at a disadvantage but it doesn’t appear to have done so.