OK, I think people aren't understanding what I'm saying, so just to be clear.

Lets say minimum wage here is £6.08 per hour (approx $10 per hour). Since decimal numbers make more sense to me, lets go with a minimum of $10 per hour for further calculations.

Full Time IMO is 37.5 hours per week (8 hours a day minus half hour lunch break), for ~52 weeks per year. So lets set welfare at that level:
52*37.5*10 = $19,500 per annum.

Everyone then is guaranteed that much. I would then phase out welfare at no higher a rate than taxation. I as an average earner get taxed at about 32% of income (tax plus NI), so cap welfare phasing at 32% too.

Then if someone who is working full time they would get:
$19,500 they've earned + $19,500 (maximum welfare) * 0.68 (minus phasing/taxation). Which is then $19,500 + $13,260 = $32,760 take home pay. As they're still on welfare they pay not a cent in taxes.

Anyone working then would be significantly better off than anyone unemployed.

Under this simplified system the crossover point is about $61k: anyone earning under $61,000 would get welfare, anyone earning over $61,000 would pay tax, nobody would get both.