Well... personally I think a lot of this depends on where the relationship is going. You refer to this man as your bf. Yes, the two of you have been dating for 5 years. But, presumably, you're not necessarily in a permanent relationship. At least not yet. You wrote that the two of you don't live together. I presume your bf is not supporting you & your daughter financially. So I personally see no reason, under those circumstances, why you & your daughter should not take a trip together whenever you choose to.

On the other hand, you mentioned your bf feels he is sacrificing time & money to build a business "for us". If that, in fact, is the case & the plan is for the two of you to blend your two families & live in-whole or in-part on the proceeds of the business, then yes I can see your bf's point. (There is, from my perspective, a "symbolic" consideration to be taken into account here.) That doesn't mean you & your daughter shouldn't take a trip together. Regardless of anything, you're mother & daughter. And getting away, just the two of you, is perfectly appropriate. But I do think it means that, if this business is in fact being built "for the two of you" as your bf contends, your trip with your daughter should be arranged in consultation with your bf.

So I guess what I'm saying is that the answer to your question really depends on where the relationship with your bf is at & what the intentions are surrounding this business he's building. Perhaps the fact that this disagreement has become "a huge argument" is an indication that you & your bf are not exactly on the same page, so to speak, with regard to the nature of your relationship. Or, in the alternative, it may suggest that your bf lacks a certain perspective with regard to the fact that although you & he may be a couple, you & your daughter share a relationship that is, & will remain, to some extent separate from your relationship with your bf. The same is true of your bf's relationship with his two children. Even if you & he eventually blend your families, he will still have a relationship with his two kids that is separate. At least to my mind, it cannot be otherwise. Hopefully successfully negotiating a compromise to this disagreement can help to clarify what it is that is going on here & help the two of you to grow as a couple. I wish you well...