This is great advice, but you also have to be really strategic about this as the solution you create to try to acquire one side of the market can easily become a full-time burden that distracts from what you really want to offer.
Using your example, the market for time tracking, invoicing, etc. is very mature and highly competitive, so if you launched a solution in this space, you'd have a steep uphill battle to gain traction.
Making something free doesn't automatically guarantee it will be competitive or appealing, especially in mature markets where the entrenched competitions' offerings are hard for upstarts to come close to parity with. Sometimes "free" makes a product less appealing.
In the example market, there are already established players with free tiers.
Using your example, the market for time tracking, invoicing, etc. is very mature and highly competitive, so if you launched a solution in this space, you'd have a steep uphill battle to gain traction.