It wouldn't work, as you had already issued the rent increase of $50 with the initial offer of a new lease (you would be silly not to as this is another 60 day notice period!), if you then issued a second rent increase of $70 it would be a void notice as you can only issue a notice of rent increase once every 6 months!
If you had given the tenant anything in writing indicating that the rent would only go up $50 IF they sign a new lease but would go up b $70 if they chose not to sign. Then increased it to $70 (when they wouldn't sign) this would probably be considered an invalid or unconscionable term which breaches the tenants rights. VCAT could then order the rent back down to the $50 increase or lower and could possibly order compensation to be paid to the tenant.
On top of all of this, you can be penalised under the legislation (5 penalty units I believe)!
Fortunately this isn't something which I have had to deal with but I have seen others go through similar.
At the end of the day - it absolutely wouldn't work!!!
