I can't concentrate on a startup, other than 2-3 hours a day because I
have to work to make a living.
What about weekend days?
In practice, an idea will take me 3 years to implement at this pace
which makes it meaningless to begin with.
I disagree. Everything depends on your demands.
I myself don't think a 3 year development time is unreasonable if you wind up with a profitable venture that returns money to you for years beyond that. People will do a a 4 year bachelors, a 2 year Masters, a 5-15 year Ph.D., etc., but 3 years to single-handedly create a profitable software venture is "meaningless"?
(Along these lines, as Anthony Robbins wrote, "People will greatly overestimate what they can accomplish in one year, but they will greatly underestimate what they can accomplish in 10 years." Or something close to that).
That said, if launch date is critical based on things like trends or competition, then either you hire out, quit your job, bag your project, get a small team of co-founders who will pitch in for sweat equity, change your idea, or hope your assessment of that launch date criticality is incorrect. Or some mixture of all of these.