This will depends whether you ahve completed your MOP?
Assuming your have completed your MOP, then is Yes you can buy a provate condo to stay and rent out your HDB.
If you still have outstanding loan for your HDB, your next bank loan will be 50% LTV, with minimum cash down payment 25%. Your stamp duty is total 10%.
Please feel free to drop me an email or call me directly for a non-obligation discussion, if you still have further questions.
Thank you & Best Regards
ERA Team Director
HP: 9639 0350
CEA Reg No. R025894Z
CEA License No. L3002382K