Buying vacant lot in Sonoma County

[Poornima Venkatesha]

Hi All,

I am interested to buy a piece of vacant land in Sonoma County (guerneville, Monte Rio area). I am considering lots that I can afford to buy with cash. Over time, my plan is to build a SFH and possibly sell it for a profit (or worst case, keep it for myself as vacation home + Airbnb if I can't sell for a good profit).

What are some of the key things to remember before jumping into a plan like this? 
What would be key things to look out for in guerneville real estate?
How much money would I need to spend to build a small home (400-600 sq ft) that I can sell ? 
Once I acquire a lot, would I be looking at a 1 year construction project or more? (including permits approvals in sonoma county)

PS: I have dealt with few rental properties so far. But this is my first time considering vacant lot and construction. 

Please share tips and suggestions and other articles that I could refer to educate myself on this topic. Thanks in advance!