See if you are talking about qualifying in any exam, then obviously you are eligible to get a seat. But the word "just qualified" that you've used confuses me a bit as I can take it in a way as just got the cutoff marks or just passed; I hope that is what that you want to say... If not, feel free to comment... As per my understanding I'll try to clear your doubt. .

If you just qualify for JEE MAINS, then you get eligible to write the JEE ADVANCE exam but chances are less that you can get a colleges through JEE MAINS. Bcoz people who score 150+ and above in Mains are the ones who have high chances to get into nits or other government colleges under 15% seats available. Now coming to EAMCET, again just qualifying marks won't help you get a seat in government college of your state, nor it will help you to get a good private college as well. The competition is increasing day by day and you need to score Good enough marks to be in the race of getting good engineering colleges. So prepare well and try to score more than the qualifying marks, probably the best that you can bring out of you.

Bestest of wishes to you. Thank you.