As has been mentioned here and on Gollihur's page, there really are no rules when it comes to the specifications of size. One maker's "large 3/4" is another maker's "7/8." Old World instrument makers knew nothing of double bass "sizes."
What is reliable is string length and body size. A 41-42" string-length is quite typical. When you get to 43-44", the intervals become quite large in the lower positions. Even with a 41-42" string-length, however, rib depths, upper/lower bout widths, shoulder slope, etc. can vary widely and be called "3/4."
My advice is to go with a 41-42" string-length and then try out a bunch of basses to find which are comfortable to play. You can also use the advice given here to narrow in on some maker's models that many have found easy to play.
Indeed, do a search here as the topic has been beaten (but, apparently, not to death

) here over the years.
Get a teacher. The DB and the EB are related, but very different instruments. A good teacher will set you on the right path in terms of technique and help you to avoid the very substantial potential for injury.