How to raise rent on 8 plex

[Casey Jahner]

I'm in the process of purchasing a 8 plex. Current rent is $500 with all utilities payed by landlord.  All the tenants are long term, some up to 17 years.  Current market rent in our small town is $600 with utilities paid.  How much would you raise rent?  I'm afraid of losing tenants and having vacant units which might be hard to fill.  Each unit has it's own meter so the tenants could pay for power (Power runs $30-75 per month depending on the unit)  What are the pros and cons for raising rent or making them pay for utilities?