How long would it take for a mans mission to the asteroid belt?

I have a idea for a short story about a single ship going to the asteroid belt to mine resources. It would be to much to explain it all here, but I will give some info. Not sure about the size of the ship yet, but it will be small. only about 6 or 7 crew, and a big room used for refinery and storage of resources... show more I have a idea for a short story about a single ship going to the asteroid belt to mine resources. It would be to much to explain it all here, but I will give some info.
Not sure about the size of the ship yet, but it will be small. only about 6 or 7 crew, and a big room used for refinery and storage of resources after extracting from asteroids, so probably the cubic footage of a oil-tanker ship.
The resources would be kept tethers to the outside of the ship till they had enough, then the equipment would be pushed to the back of the room and and resources brought inside to be taken back.
No Inertial dampeners, they are subject to the same laws of motion as anyone else.
No warp drive. they can only go as fast as the ion-drive can push them.
and I know it would be slower on the return trip due to all the added mass.

Just from my imagination I was thinking 8 months to get there, 7 moths of work, and 9 months to return, so each mission would take 2 years.

After thinking about it, not sure if a ship could go that far in 7 months, or maybe they could get there much faster,
I tried to look online, but was finding times from 70 days to 3 years just to get there, I am hoping someone can give me a good estimate.
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