How can i tell if he's ready to get married?

my boyfriend and i have been together for 7 years. i have a daughter that isnt biologically his but he takes care of her just like she is his and she calls him daddy. we have lived together for 3 years. my question is when i bring up marriage he gets ill and acts like he doesnt really wanna talk about it. he says the reason for not marrying me yet is the money issue. i let him know that i dont want a fancy ring or wedding i just want to be married. so whats the deal do you think he really just doesnt want to get married or is it really the money issue?