It might be a little more expensive than if only one of those countries held it. The World Cup is rich though, and definitely would make their money back. It would be cool to see the two different cultures of fans. It would be nice to compare Britain to Ireland. I think it would be good for the sport of soccer.
Yes, I believe that England and Ireland should co-host the World Cup in 2018, because the World Cup should move around. Africa hosted the world cup with a great deal of success, and it's time for the World Cup to move back to Europe. Hosting it in many places keep member nations interested, and gives the players something to look forward to.
I do believe it would be a great spot to host it becuase it would also make a great place for tourist to visit. I know that if I could afford it I would try and go and see the world cup and its in the country I want to visit most.
The location of the 2018 World Cup was decided in 2010 to be Russia. Not much else to say, except that if England or Ireland wishes to host a World Cup in the near future, 2026 would be their goal, as the 2022 World Cup is in Qatar. Why did nobody google this?
If Ireland can achieve sovereignty by 2018, my answer would still be no. You can only hold the World Cup in one arena. Unless you want to build two stadiums that sit on the borders of each country and bus the players across the border at the half, they should not share the cup. Also, this would be a great thing to do for a newly formed country, so I would say Ireland still not share.
I do not believe England and Ireland should co-host the World Cup in 2018. I believe it is better to have the event in one location that easily accessible to all parties. I believe splitting it up would cause problems that aren't necessary. I think they should pick one and then visit the other in a following series.