Out of curiosity I just checked to verify that you can hire mercs, save scum their traits if you want, dismiss them, and then go pick them up again later and they'll keep those traits you save scummed. You can also take their stuff. So Felix and Space Marine both get you combat armor for cheaper than actually buying combat armor and Connor gets you duraplate for a LOT cheaper than actually buying duraplate. Enya gets you a power katana. You don't really get anything for Ayden so you're basically paying $4000 up front to lock in his traits for when you hire him back again later. You could certainly go pick up Felix and/or Ayden and use them to capture those melee monster slaves before dismissing them. They would do that a lot more effectively than some random scrubs you captured on day 1.
I think rather than insisting on zero salary I would pick up the top tiers to take their stuff and lock in their perks, use them to pick up the melee monster slaves, and dismiss them but hire all of the other mercs and keep them. Several of them have the actual scavenger perk, Dexter has enough science to be a good quartermaster, Aiko makes a great head maid or nurse, Armand obviously more than pays for himself as an accountant once you have a few investments, etc. The top tiers make up something like 90% of the total salary cost you'd pay if you hired every merc so if you just skip all of the top tiers for the first several months of the game you get most of the benefits of all the mercs for very little salary.
Almost forgot, you can very easily capture an abomination on day 1 from the place you pick up Laika and Loden. Those guys start with 400+ health and strength/stamina way beyond the caps as well as high melee skill. I wouldn't want to use one in combat long term since they can't use weapons and they cause influence loss with every individual fight they're in, but they CAN wear armor. So they could be an interesting day 1 option for someone who for some reason did not want to ever hire any mercs. Once you take out the space hulk group you might also find it amusing to create a full party of abominations and go clear the town with your zombie army instead slaves or mercs.
Just tried the above option in my latest game, hiring all the top tiers so I can easily round up the combat slaves. It's day 6 now and I have Cassius, Truls, Kate, and the ex Arena champ as my combat party now plus all of the mercs except the top tiers, Dexter, Loren, and Doyle for a total salary cost of $159 a day. So I'm already passively profitable with just the few slaves I have working random jobs. Connor and Felix donated their armor to the cause so I have some free Duraplate and Combat armor for Cassius and Truls and will be getting a stealth suit for the ex arena champ by sometime during day 7. Cassius and Truls both have Greatswords, as does MC (had to buy those). Kate and the ex arena champ have katans (both free). I'll pick up Loren and Doyle soon, just hadn't gotten to it. Not sure about Dexter since Averil rolled Techie so she works as a quartermaster.