付现 is a verb-object compound (离合词) meaning 'pay in cash'. As a separable verb, it can be split: the verb 付 can take aspect markers or complements, and the object 现 can be modified or quantified (e.g., 付了现 'paid cash', 付一次现 'pay cash once'). In non-split form, it functions as a single verb. Note that 现 here is short for 现金 (cash).