as for mini hydro power, depends on "how small it is". if you want to build the size of miniatures, it would be very easy to create from scratch, even from very cheap materials. nevertheless, if you build that for "small community", you might want to look for how much energy you will produce (electricity for sure), from there then you can start to design how big your power plant will be. The next step then is also to calculate the water debit. It will be much much easier if there's big waterfall nearby so power generation is not really a problem.
Thanks @ Elhadi. @Gabriel your material is highly useful. @Qoriatul, I appreciate your laudable contributions. I got issues translating the useful materials to English language. Can you please help?
Herewith is a compilation of the top-50 most cited articles on mini hydro in the last 50 years from the Thomson Reuters ISI Web of Knowledge comprehensive database. Attached is also the endnote references data for your records. Good luck.