Unless you have a regular source of income that covers all of your product development spendings, you'll have to continuously make sure you don't overspend. This has hard consequences: postpone work that isn't top priority, be frugal when dealing with salaries, focus on revenue growth instead of quality.
|Bootstrapping a startup requires to make hard choices to preserve your cashflow!|
Cashflow is king for most startups: even if you hand team problems skilfully, maintain a upbeat pace compared to competitors, money problems are still able to kill your business relatively quickly.
One way of handling this is to have several regular revenue streams that make it possible to invest in building a quality product over time even if you don't get any funding. Stable resources are the key to a sustainable product roadmap!