Blase,
I'm a REALTOR in MA and am with Berkshire Hathaway HomeServices Commonwealth Real Estate. I can speak to what I know, I pay for E&O Insurance, MLS dues, and REALTOR dues (required by BHHS) and this all costs about $1200 annually. No desk fees, no marketing fees, nothing else required.
As for the splits, that depends on what your production value is and how you intend to use your license. My brokerage starts new agents at 60/40 and it goes up to 90/10 based on production. Once you reach a threshold amount (capping out) you are charged only franchise fees per transaction that are nominal.
If you are primarily sourcing and analyzing your own deals, you may want to find out what the minimum franchise fees are within brokerages for transacting your own deals. Otherwise, you might want to consider writing your split out of any offers to increase its value to the seller. While the closing cost is to the seller, the net could be more to them and favor your offers over others having to pay a buyers agent split.
I'd mimic some of the commentary that the brokerage you choose largely depends on what you want to get out of it. In MA you obviously have to hang your license somewhere to do business. I will say that for BHHS Commonwealth Real Estate you get a reputational brand, great tech stack, good training and resources. I looked at a KW team and that wasn't my thing and talked with people within Sotheby's, Compass and Coldwell.
Let me know if this helps!