How should I heat the upper level of my 2-story investment home?

[Benjamin Trumbull]

I'm in the process of purchasing a 1890 2-story home with basement and double detached garage. The purchase price is 95k and the average value of homes in the neighborhood is at around 145k. I plan to make this my home for 5 years and sell it (or possibly rent out). The basement and main level have hot water baseboard heating throughout but the upstairs does not have anything for heat. There is a brand new ac located outside and air handler located in the attic. My HVAC priced me around 3k to bring 3 hot water baseboards to the upstairs, along with a few other things. He said this would be the best option and electric baseboards just wouldn't be efficient.

My question is, for a 400sf 2bed 1bath upper level, what is the best way to heat this? Considering I'm not planning on living here for over 5 years. Thanks.