Mining in 2019

[Rose_btc]

I think if you shift your question to Mining speculation session or read thread of that session to will get better idea. And reading the threads in that session can give you broader perspective about the prerequisites and challenges of mining.

Here is the link of the session:
https://bitcointalk.org/index.php?board=81.0

[wwzsocki]

Antminer D3's can't compute SHA-256, it's designed for X11 algo of coins like DASH and copy-cats/forks
Forget the chance to mine a block, can it even mine Bitcoin at all?...

You are right I made a mistake it was one Antminer S7 and two S3, not D3. I got them for free from my friend Crypto Mania and started to play with it.

They are still mining because I handed them over to another crypto enthusiast who wanted to start his mining journey  .

As for now, they are running and my friend still counts to find solo BTC block, but I rather doubt that this is possible.

[Velkro]

And if it does how much time does it take to pay off equipment and electricity.
Isn't it simpler if you trade cryptocurrencies instead of mining them?

On the second question.... YES!!! Its nothing compared to knowledge you need to mine.
Question about paying off should be only you to answer yourself based on your electricity price, coin you mine and scale of operation.
This is professional business with huge players and amateurs have to be REALLY prepared well to have any chance in that market.
Easiest is to just buy and hodl or trade.