My main question was if I could get at least a ROI for my rig if I start mining right now. that's what worries me most
Nobody will be able to give you a YES or NO answer because there are so many factors that need to be considered. You may be the best person to answer your question once you are able to compute all your costs, expenses, and projected revenue.
The best I can do to help you is to say, I believe its work the risk.
Unlike investing directly into buying the coins, building a mining rig means you have an asset that will not suddenly disappear. You don't really need 100% ROI when you come to think of it because GPUs will never lose value esp. the newer ones. They have other uses other than mining and gamers will always be there to buy them from you.
