Make your plan, map it out, understand the financial impact that some vacancy, turnover and unit refurb costs will have on your cashflow and decide the pace that's right for you.With a staged plan to raise rents slowly or force some turnover by not renewing existing leases, I'm sure you can get the rents up to market within six months to a year.Good luck!

After the first year, I didn't collect another time upon renewal.

If it coming up soon to renew, you could just choose to non-renew and they would have to vacate within 60 days. 

I am looking to renew the leases and increase the rents to market value.

If they don’t renew their leases I am considering going another route and offer seller financing.

At the end of this contract extention can I refuse to renew and get my good faith deposit?

It has all the usual suspects - large relocation fees if you don't renew a lease, fixed % of annual increase.I intentionally rent under market, but will be forced to immediately raise rents if rent control goes in place to protect the long term value.

This decision is not easy so I just renewed my leases, and keep the rents coming until next year.

This definitely renewed my drive to make this happen! 

They can afford the monthly payments but don't have the downpayment for the house saved yet- they have a plan to do so in the next year.We offered to allow them to rent at a lesser rate for a year (to help them save for the house) and they be responsible for small repairs and at their lease renewal we touch base and see if they want to buy.