Your potential legal costs should always be considered before starting any legal action. So, make sure you get advice on the risks of winning as well as the risks of losing.
In our common law system, "costs follow the event". This statement does not mean that you will recover every dollar spent on your lawyers. Quite commonly, parties who get a costs order after winning judgment in an ordinary breach of contract case only recover between 60-75% of their costs.
Frequently, if a judge is not given sufficient information when making an order for costs, they will order costs "as assessed or agreed".