On spec
Definition 1 of 1
Pro Tip 1/3Risk Involved
Using 'on spec' suggests a risk, as effort is given without guaranteed payment or success. 
She wrote the article on spec, aware that it might not get published.
Pro Tip 2/3Business Hope
'On spec' often expresses hope for future business or recognition from the recipient. 
The architect drafted the plans on spec, hoping the firm would hire him.
Pro Tip 3/3Informal
'On spec' is commonly used in informal business contexts, not usually in formal contracts or agreements. 
They built the prototype on spec to attract investors.