If you shop parts, you should be able to assemble a a quality AR for around $600, and you are not going to find a new Mini for that.
I would start with Palmetto State Armory. I was able to obtain one of their "blem" lowers for $60 plus shipping and transfer. From then on, it was wait for the sales.
Receiver + shipping + transfer = $90
BCG + LPK + shipping = $160
Premium Mid Upper + shipping = $315
Milspec collapsable stock kit at the gun show = $40
I did all this with new parts. If I had been willing to shop the equipment exchages on the various gun boards, I could probably have brought the price down to around $500.
You will still need a rear sight, but there are some viable options out there for around $25.
Don't count the AR out. I had one for about 10 years before I traded it in on my first AR. I wish I hadn't wasted that time.