What exactly are "all closing costs" investors promise to pay

[Benjamin Cowles]

so I've been writing in my letters that I will "pay all closing costs" just because that's what I'm supposed to write right? If one wants to be a real estate investor that is what one offers at a minimum right? Well I have yet to discuss these "closing costs" with any seller but I'm just starting to wonder what exactly am I talking about saying I'll pay "all closing costs". I feel like the first deal I do will come with a scroll of "closing costs" some items of which may surprise me. Should I be prepared to "pay all closing costs" or should I be on the lookout for strange items like seller's grocery bill or something? Do you as investors offer to pay all closing costs and if so how do you know exactly what you're willing to pay if it's not everything that's in the bag labelled "all closing costs"?