Here are a few ways to combine 있다 and 오다. 1. 오다 + -아/어(서) 있다 -> 와 있다 / 와서 있다. (와 있다 is much more common) * 와(서) = has come; 있다 = be/stay in the place; 와 있다 = has come and is ready/staying. (왔어 있다 doesn't exist) - 언제부터 와 있었어요? = Since when have you been here? [have you waited?] - 내가 도착했을 때 친구는 벌써 와 있었다 = My friend had already arrived when I got there. (phrases related to waiting for someone) - 언제부터 기다리고 있었어요? = Since when have you been waiting? (언제부터 = since when) - 온 지 오래됐어요? [한참 됐어요?] = Has it been long since you came? = Have you waited long? (오래되다 = has been long) - 오랫동안[or 오래] 기다리셨어요? Have you waited a long time? (오래 = 오랫동안 = for a long time) - 언제부터 여기 (와) 있었어요? = Since when have you been here? (these two are used less often) - 오래전부터 기다렸어요? = Have you waited long? (this is not used as much) - 오래전에 (나)왔어요? = Have you waited long? (this is not used as much) 2. 오다 + -고 있다 -> 오고 있다. * 오고 = coming; -고 있다 = is V-ing; 오고 있다 = is coming - the present continuous tense. - 저기 영철 씨가 오고 있네요 [or 오네요] = Look, Youngchul's coming over there. - 새 시대가 오고 있다 = A new era is coming. 3. 있다 + -아/어 오다 -> 있어 오다. * 있다 = exist, happen, occur; -아/어 오다 = has been V-ing (like the present perfect or PP continuous tense in English) - 이것은 옛날부터 있어 온 일이다 = This is something that has been happening for a long time. - 이런 일은 옛날부터 있어 왔다 = This kind of things have been happening since long ago.