Instagram Questions: Safely Buying Account and Posting Numbers

How to safely buy one account?

I got a guy selling it, and i dont know him ( not BHW related, sorry if cant post it here).
Im sure it's a crappy acc:
10k followers that he got it by using "Mega Followers" instagram group in Brazil, one post until now 7 days old with only 1 likes.
The acc has her personal photo with a post with anime (Itashi Naruto) and only 15 likes.

If i want to buy any account, how to do it safely ?
I should askto get (own) the email too?
I fear that he just change the password faster than me and then i could lost my money. I dont know him.

Another question:
How many posts i should do with an account 3k Followers / 1kFollowing ?
Niche: Brazil Music/ Culture .
My bot control it and do 7 posts/day with hashtags with 10k - 30k posts.
Im getting 50 likes on bad posts, 200 on good ones and i hitted 900 on post with a girl showing the low part of his tits (sorry girls).

I unfollow 1000 users on 4 days ang got my account blocked for likes/follow/unfollow/blocks.
Posts still running.
Any advice for this situation?

i can show the account if anyone is interested to see.

(im not using google tradutor, sorry for the english)

Thx guys !

edit: Im not selling anything on the acc. Is there any spotfy afiliate ? i think it should do good

Up !

That account might be shadowbanned.
And then,yes you should own email,but then question,lets say he used gmail,gmail is easy to restore I think. A lot of scams is going on around with social networks because gmail and other platforms is pretty easy to restore. It must be good source @ seller otherwise its probably a scam.