Joining the European Economic Area is not without its problems. Doing so would give the UK unrestricted access to the Single Market, but free movement of goods and people is a non-negotiable precondition of membership. Additionally, we would still have to apply the EU rules that govern the Single Market, without having had any input when those rules were being drawn up.
As part of the EU, we are currently part of a customs union, so there aren't different reporting obligations on UK companies in terms of tracking what the VAT rate is in different member states - there is a common external tariff and importing/exporting is relatively simple. Within the EEA it's a completely different VAT regime, and the burden of the extra paperwork will be quite large for small and medium sized business.
Those SMEs were already very nervous in the run-up to the referendum. The latest figures show that they are collectively sitting on £164 billion in current and deposit accounts rather than spending on investment - a seven per cent increase on last year.
It has been argued that a temporary increase in unemployment would be a price worth paying in the short term for longer term gain. However, any increase in unemployment is a considerable 'double whammy' to the nation's finances. In the last Financial Year, 54% of the total HMRC tax receipts came from personal taxation; Income Tax, Capital Gains Tax, National Insurance Contributions and Bank Payroll Tax. A further 22% of total tax receipts came from VAT. Unemployment not only considerably reduces the amounts collected from those two sources, but also increases government expenditure. There will be an emergency budget soon, despite the Brexiteers saying that there wouldn't be. An increase in taxes - direct and/or indirect - is a very real possibility. (Brexiteers need not respond to this latter point - I have already predicted what those responses will be!) The next change in interest rates from the Bank of England is likely to be downwards - it is charged with economic stability and keeping inflationary pressures low. A week Stirling will result in more expensive imports; it won't be long before these are being reflected on the High Street and the garage forecourts.
The UK would only have control of immigration if it did not become part of the EEA and instead negotiated free-trade agreements or relied on its membership of the World Trade Organization. The latter is not without considerable risks, and the former will take a long time, despite the best promises of Nigel and the Brexiteers. (The worst boy-band ever?

) When President Obama said that the UK would be "at the back of the queue" on negotiating such deals, it was dismissed as "scaremongering" by the Vote Leave camp. Bilateral trade with the United Kingdom acounts for just 0.7% of U.S. G.D.P. (Yes, that does say 0.7% - it's not a typo.) UK exports to the USA last year were around $51 billion. The US isn't going to lose any sleep about losing 0.7% of its GDP, but if the UK loses $51 billion in exports that's gonna hurt.