Need advice: how can I finance my carriage house?

[Devan Johnson]

BP experts help me out!

Situation: I own a home in a pretty prime spot here in Colorado that is zoned for two residences. (Super rare and super lucky)

My plan is to build a carriage house above garage 600 sq ft, 1 bed/1 ba.

Cost to build: 150K

Assuming Rental income approx $1100/mo (conservative)

Currently owe 290K on current mortgage (4.1% 30yr)

80K cash on hand

Everything is ready to go: architecture, engineering, permit is almost ready to submit. 

I'm having trouble financing this project. Open to suggestions. HELOC? cant get get enough out of that strategy ( at 80% LTV)

Construction loan? terms don't look favorable. Plus I'd end up refinancing my entire current mortgage at a higher rate ! (because rate have gone up)

Thanks in advance!