Sell and double my money or hold!? Help!

[Ethan West]

I bought a 40 acre farm property 3 minutes from town last July for $367k. I have put $275k into improvements. 

I’ve had several brokers out last week and all of them have given me comp reports in the $1.2m to $1.3m range. 

There is a Costco, Fred Meyer, other stores being built down the street this next year. A hwy frontage road is also being discussed. There is really no property especially this size around. 

I’m confused if I should sell and double my money. Or if I should hold and slowly keep improving I.e. build a house. I feel like it’s sell now or plan on holding for 7-10 years?