Buy when the workflow is common and speed matters.
Standard products are usually the right choice for common needs such as accounting, commodity scheduling, payments, basic CRM, or document storage when the business can adopt the product responsibly.
A mature vendor may offer capabilities, security operations, support, and integrations that would be unreasonable to reproduce for one business.
Build when the limitation is operationally expensive.
Custom software can be justified when teams repeatedly re-enter data, cannot support business rules, lack owner visibility, or lose customer opportunities because available products do not fit.
The workflow should be stable enough to define, important enough to own, and valuable enough to support after launch.
Consider integration before replacement.
Sometimes the missing capability is a portal, dashboard, workflow, or reporting layer around existing tools. That can preserve trusted systems while removing the most expensive manual handoff.
Provider access must be verified. The plan should include fallbacks when an API is limited, delayed, or unavailable.
Document the decision and revisit it.
Record the workflow, alternatives reviewed, cost assumptions, integration findings, risks, first-release scope, and support model. This prevents the project from being driven by a demo or a feature list.
Revisit the decision when the business changes locations, volume, staffing, product mix, or reporting requirements.