Go big scale

Me & a friend were thinking about getting into bitcoin mining and we are doing the numbers and spending around 8 - 10k on a setup and it would take 3 years for return on investment. even after ROI is met we will only be making around 300 to 400 a month. OR We can spend 80,000 + and make a few thousand a month. My question is, in this volatile market would that be a wise investment? i know its hard to predict but i want just a opinion from people that have been dealing in this market for some time.

You can cash out wherever you bought the BTC. It's simply the reverse process. If you decide to use Coinbase, consider doing it on Gdax instead. You should get better rates there and since it's part of the same company, your Coinbase account can be used on Gdax as well.

Be prepared to face some extra KYC/AML questions as you try to withdraw your funds to your bank account. $1M+ will raise more flags than what you originally spent on buying the coins. In addition, notify your bank in advance of the incoming transfer to prevent them from freaking out.