I have been using Lenovo a6000 from 3 years and completely satisfied with my experience since I got a new one I’ve gave to my father and have no complaints. Lenovo a6000 was a budget package with 4G LTE support way before jio 4G was released. It was a popular phone back then supporting 4G. I have no issues with the battery camera performance, Storage since I have been using the phone.
I mean who would give such a great package with 2 GB ram 16 GB internal and four 4LTE support in 3 years back
If you would go for J2 or some other phones then Lenovo a6000 is way better than J2. I would advise to buy Lenovo a6000 if you are looking for a good budgeting second hand buy. It will cost you around 2500 and would be a great experience.