Hi
I am conducting research into the cost of mining a block and the effect this cost has on transaction fees.
Please let me know in this topic whether you are interested.
http://www.coinwarz.com/calculators/bitcoin-mining-calculator has your answer. And its random, finding a single block that is. So it could be seconds, or years for a single person.
No idea what you mean by "effect of finding a block on transactions fees" a single block doesn't change much, but it will include TXs out of the mempool, if several blocks are found in quick succession, lower TX fee may more easily be included at that time, but it doesn't change the TX fee overall. And the TX fee is not arbitrary, you could try a TX with 0 fee as well, or 1BTC.