A bar or nightclub owner may have, initially at least, access to a number of "luxury" items - alcohol, tobacco, drugs, women, as well as a range of contacts they might be able to call on, and be well known within the local community, all of which may come in useful when empire building.
On a related note to the bar / nightclub owner, I don't know if you intended to include this under security companies, but in the UK it's common for bar / nightclub bouncers to work for specialist companies who then provide doormen to pubs on a contract basis, so someone who owned one of those companies would potentially have access to a number of people who are well used to trouble. In some cases the same companies also provided stewards for concerts / football matches, etc, so have hundreds of people on their payrolll (for many it's a second job opportunity and / or a chance to get into events for free).
Probably too obvious, but pre war politicians might be an option.
A charismatic university professor perhaps? Possibly one who has studied / taught certain periods of history that may have given them some knowledge / insight that may prove useful in the T2K World? For example, someone who is a subject matter expert on the medieval World may attempt to use their knowledge to recreate some sort of feudal State with themselves at its centre?
Ultimately though, all you really need is someone particularly charismatic who is ideally a good orator as well. When I put my Alternative Survivor's Guide to the UK together I made one of the major marauder leaders a former call centre worker who manoeuvred himself into being in the right place at the right time
http://www.twilight2000files.com/page702.html
Another was a student nurse before the war
http://www.twilight2000files.com/page72.html
So whilst some career paths obviously offer an advantage in terms of having resources / people already in place, I think pretty much anyone could end up as a warlord, particularly in areas where there is a mass movement of people leading to refugees overwhelming established communities.