After watching those videos it does look pretty straight forward. I’ll have start researching the best parts.
Since you mentioned that you might be interested in also having a general use PC, you might want some modifications to typical mining-specific builds:
Budget/low-power CPU
Motherboard with many PCIe slots, often a mining-specific board, but they definitely don't have to be.
Minimal amount of RAM (4GB is typical, 2 is *usually* okay for a dedicated mining rig)
At least one PSU (never skimp on quality here, stick with power supplies that have their guts made by reputable OEMs, such as Seasonic, SuperFlower, FSP, etc.) Units with their guts manufactured by mid-tier OEMs (such as Channel Well and HEC) are usually okay, but not as reputable. Stay away from ones mostly unheard of. You can use multiple power supplies, but keep in mind that balancing the load nicely isn't always easy, depending on your system configuration. Additionally, you do create another point of failure; if either unit fails, your entire system may experience downtime until you fix it, depending on which PSU fails.
Boot device: Flash drives are fine for a dedicated mining rig, small SSDs are usually nicer. I just use whatever I already have (old 80GB HDDs, flash drives, unused SSDs)
Graphics cards, up to you. Balance price:performance (hashrate/$), efficiency with electricity (hashes/joule), and rig density (max hashrate you can get out of one set of a motherboard/CPU/RAM/etc.).
For your rig to also double as a general-use desktop, you may want a higher-end CPU, 8GB+ RAM, and a larger SSD or HDD. Don't forget to have some kind of frame or enclosure planned, since most standard desktop cases will not accommodate more than 3 graphics cards, and that's with a very poor cooling situation. For a single rig, DIY open-frame builds are usually the best way to go, but it depends on your needs. (Do you have inquisitive pets/children? Is noise a problem? Etc.)
I want to ask how much capital is needed? whether to build the rig you suggest will be profitable? Thank you in advance
Everybody wants to know those things, but they are situation-specific. Capital is the simplest to predict, all you need to know is what hardware you want to purchase (and how big you wish to go), and how much those components cost at the time you wish to purchase them.
The second question, on profitability, is extremely difficult to predict. If you have negligible electricity costs or electricity costs that are independent of use, AND you can reasonably assume that, after a few months, you could resell your hardware for close to the price at which you bought in, AND you can reasonably assume that the cryptocurrency you choose to hold will not crash significantly, then you will most likely profit.
As you have likely read already, mining is not a guaranteed get-rich quick scheme. Mining difficulty, exchange rates, etc. are all varying wildly. The best you can do is assess your power costs, expected initial investment, your confidence in certain cryptos, etc. and then reach your own conclusion.
The general advice for a profit-oriented rig is to avoid spending unnecessarily on components that do not contribute directly to your hashrate. (Choose a cheap CPU, minimal RAM, etc.) (And having a quality PSU is almost always considered a necessary expense.)
For example, if you built an entire rig from scratch only to host one 1060, it will be rather difficult for that one card to pay off the entire costs of the other components, since that overhead cost is so far out of proportion to the ability of actual mining device to produce revenue. If you build an entire rig from scratch to host, say, 6x 1060, then you are getting a superior rig density, and should have a better chance at paying back the cost of your graphics cards, and the base components, save for the additional risers and PSUs required. (I.e. minimize the
proportion of funds spent on non-mining components wherever possible without sacrificing functionality.)
Note that the OP expressed a desire to have a general-use desktop, and not a dedicated mining rig, so it's not purely $-oriented, since the expectation is that the OP would benefit from having that desktop system, in addition to being able to mine.
I do have a dog. She wouldn’t bother it though. She mostly lays around. I was thinking 1070’s for the gpu’s and I thought about designing my own frame. I own machining equipment so I shouldn’t have a problem making it. I’d have to figure out the noise part. My wife probably won’t want to listen to it all the time if it’s loud. I’ll just locate it in a different part of the house. Hopefully it’s not too bad. Time to start making a list. 
