That the expenses are delayed, that the expense rate for travel may hardly cover ensuring the tyres are at the correct pressure ... depending on the miles travelled ... that there could be outgoings for eight weeks before expenses paid ... that its not possible to make employers understand that parking eye is to prevent the employees from parking in the customer car park ... and lots of other inputs that can bring down self employment - perhipheral, supply and contract workers and not the least of these complying with the Highway Code and Road Safety.
That creating a cash flow forecast on the worst case scenario is probably a must before taking on any casual, perhipheral, supply etc work as that is most likely to happen - plus more unexpected hiccups.
This includes the contract for resources to be made for dodgy places offered by a local college which could have compromised personal safety.
There are some very dodgy practices in the big wide employment world in the UK at the moment. Its one thing to be savvy as HR but there are ethics and good practice and H&S issues etc. that should be honoured.