New owner/old tenant - Asking for additional deposit

[Garry Deihl]

I'm expecting to close on my first home in about a week. I'm buying a side-by-side duplex. I'll be living in one side while a tenant who already occupies the other side will be staying. Tenant has been paying $650/mo, which I will be raising to $700/mo, which is at the low end of comparable area rents ($750/mo if tenant wants to use garage, which is having a new door and opener installed, and use electricity from garage to charge his hybrid car). I'll be giving at least 30 days notice for the rent increase. The tenant also only has a $250 security deposit. I want to raise this to the equivalent of one month's rent. How should I go about doing both of these things without making the tenant upset enough to leave? From what I have seen and know about the tenant, I would like to keep him, at least for the time being. Any advice or suggestions would be appreciated.