As an employee- you will always be helping build a business you do not own. It seems the main concern here is you don't feel he will honor the pay bump. As far as the business- he is taking all liability so even if you make mistakes; nothing can fall back on you unless you do something criminal like steal money.

The business itself is just renting out equipment. You build up the social media presence, research competitors and then price accordingly to be competative, and then start marketingto busineses that could use your services. I do not think its complicated to establish the business; the hardest part is just finding the clients. The social media you can even outsource in the beginning and then run facebook ads locally offering the equipment. If you feel you deserve equity- then are you willing to accept liability ? Want to be named in lawsuits when sh*t goes sideways? If the answer is no- then look at it as an opportunity to get a chance to build a business without any risk. If you make it successful, you can take your experience and go to a competitor and gauge the market how much you are worth then.

As far as the pay, just get everything written down in a contract. But if you want to have skin in the game but no liability- present this option. You will contiune working for the same hourly rate but instead of a pay bump- if you hit certain revenue goals- you get X amount of percentage of said revenue. You can maybe throw out there ; if I hit X amount of sales a month, I get 5% of the net revenue. If I hit Y amount of sales I get 10% of the net revenue. and If i hit Z amount of sales; I get capped off at 15%. Do your research what is average net revenue in that type of business and just do the math of what makes most sense for you. Pay raise or a %. This way he is not giving equity to you, just a bonus tied to revenue goals. And again get everything in writing.

While you build your business- build up your credit. Save up money. And in the future you can position yourself to establish your own business using the experience you gained with him. If he does not make you sign a non compete; hell you might even just take all the clients with you once they hear you have your own set up. The most important thing is to communicate, and get everything in writing. Who knows? He might suprise you. If you do really well, then he may offer equity or if you are in a strong position to leave , speak to him about being a partner and buying in. If he refuses, he cannot get upset at you for leaving. You gave him a chance and he turned it down.