1 Sam 9.9
8 The servant answered him again. “Look,” he said “I have here in my hand a quarter shekel of silver. I will give it to the man of God, and he will tell us our way.” 9
(Formerly in Israel, a man on his way to inquire of God would say, “Come, let us go to the seer,” for the prophet of today was formerly called the seer.) 10 “Good,” said Saul to his servant. “Come, let us go.” So they set out for the city where the man of God was.…
2 Sam 24:11
10 After David had numbered the troops, his conscience was stricken and he said to the LORD, “I have sinned greatly in what I have done. Now, O LORD, I beg You to take away the iniquity of Your servant, for I have acted very foolishly.” 11
When David got up in the morning, a revelation from the LORD had come to Gad the prophet, David’s seer: 12“Go and tell David that this is what the LORD says: ‘I am offering you three options. Choose one of them, and I will carry it out against you.’”
1 Sam 8:18
17 When Samuel saw Saul, the LORD told him, “Here is the man of whom I spoke; he shall rule over My people.” 18
Saul approached Samuel in the gateway and asked, “Would you please tell me where the seer's house is?” 19 “I am the seer,” Samuel replied. “Go up before me to the high place, for you shall eat with me today. And when I send you off in the morning, I will tell you all that is in your heart.…
Amos 7:12
11 for this is what Amos has said: ‘Jeroboam will die by the sword, and Israel will surely go into exile, away from her homeland.’” 12
And Amaziah said to Amos, “Go away, you seer! Flee to the land of Judah; earn your bread there and do your prophesying there, 13 But never prophesy at Bethel again, because it is the sanctuary of the king and the temple of the kingdom.”…
Then there is Hemen, Hanani, Jehu... the list goes on and on...
These were legit ministries that God used in OT times.