simple formula;
add 5% for purchase costs.
Then, multiply this amount by your interest rate; $420k x 7% = $29400 p/a.
Divide by 52 for weekly cost of finance = $565 p/w.
expect 20% of rent to be eaten by costs. This allows for 2 weeks vacancy as well.
$500 x 20% = $100.
nett rent is more...