When the UK leaves the EU what affect will it have on Ireland over all?

I hope a Hard Border between the UK and Ireland

As the NI/ROI border is a unique border AND because of the Troubles of the past where there was a hard border ( barriers/customs/police/garda control) now and over the last couple of decades it is open AND because of the 100 yr freedom of movement of Irish/British citizens.....this alone causes issues the EU have nothing at all to do with freedom of Irish/British citizens but as ROI will still be in the EU it will/could be used as a border to cross by EU citizens to illegally enter NI ( UK) it could be used to import/export goods either way which breaches EU and UK tax laws/customs laws, certainly NI/ROI don't want a return to past violence/terrorism and terrorists take advantage when they can of any changes that allow them to, NI/ROI do not wish to lose their 100y freedom of movement or be stopped daily ( hard border) when there were cross border road improvements there were 10 miles queues twice a day in both countries which both country suffered economic loss as daily there are thousands of Irish who live in ROI and work in NI and same other way. The EUs suggestion is the "back stop" which answers lots of the issues BUT it also separates NI from Britain and the NI do not want that they wish to remain British and under British laws and the back stop is temporary so all that is happening is putting off a situation that needs resolving until 'later'.

It will cause lots of issues on the island of Ireland...ROI purchases lots of goods from the UK, that will cost them more money to continue and if they get them from other EU countries it will cost them more..so just like when the ROI took on the Euro prices will rise again for the ROI public.

The intention is that the border operates with little change. It is quite feasible that electronic customs checks can be applied, where necessary. In general, reputable firms can be trusted to move goods already approved for import/export by declaration in advance online. The whole matter has been deliberately exaggerated by 'remoaners' who long to cancel Brexit.

Depends on the type of Brexit. From no meaningful effects to all Irish Republic imports and exports needing to be from mainland European ports.