I just started playing D&D 5th edition at college with friends after playing ad&d for years with my family in a homebrew campaign. I just noticed that fighters don't get any followers after getting to level 9 in 5th edition. Are there any mechanics for having followers in 5th edition? I'm playing a noble dwarf so I was hoping to have a small army after level 9.
Yes there is, you hire them. Maybe you hire a group of NPCs to go on a side quest for you, or to research this or that spell, or go find these items that we need for our main adventure.
You can even hire someone to build you a castle if you have the money, and you can fill it with servants.
Nothing has really changed other than it's not automatic. If you have money, then hire followers.
Page 159 of the PHB mentions the use of hiring services, and describe very generally hiring mercenaries or spellcasters, but not so much about how to handle them. Since they are NPCs that's more the domain of the DM.
In the DMG between pages 89 and 97 are some bits about NPCs both friendly and villians, and it has a section on NPC Party Members beginning on page 92, here it goes into more detail about managing NPC Followers, but the material is more for the DM than it is for the players. Things like how loyal is the NPC to the players.
Your DM will tell you what he or she wants you to do, whether to build your own NPCs or let her do it.
So mention to your DM that you are interested in taking on an apprentice, or acolyte or squire.
One of the things that's changed also is character level versus class level, so different sorts of followers are attracted to different classes aren't they, but what now with the new character and class level mechanic? At level 9, I presume you are just as famous whether you are a level 9 paladin, or level 5/4 fighter/wizard.
So anyway. Talk to your DM, and see if you can hire an apprentice or a team of NPCs to help you on your main or side quests, or to build and make stuff on your behalf while you are away.
To complement the answers above, the variant noble background gives the variant feature of retainers:
(PHB 136), three "attendents or messangers, and one might be a majordomo."
Is this an army? No. But they are followers who would be useful in maintaining one.