Wanting to explore other options or find out other financial strategies for trying to build a detached home on our lot without having to refinance out of our 2.75 interest rate with a cash out or doing a HELOC.

If you have a questions feel free to reach out regarding management, and services needed to run a successful STR.

Heloc I think we could get $175k, maybe DSCR, I am a veteran with service connection disability rating 40% but with my mortgage and car loan not sure I could make debt to income work.  

If for some reason you are unhappy with eviction/RE attorney, let me know I have someone that i great (and I thought her rates were fairly reasonable for the nightmare eviction I had to use her on).

Any pitfalls to avoid or tips for making it a success?

The success of your rental depends on it.

I have a million classified posts showing the style we build. you'll never get the numbers at that rate. your numbers are way off and way too low. work with an experienced general contractor who knows this stuff. 

I made quite a bit on it and it was a complete success.

BTW this will also help you understand local rent rates.

Those two together create equity.Here's what I want you to understand about “buy and hold” residential real estate:Let’s use a single family home with a property value of $300,000Let’s use an initial loan amount of $240,000Let’s use an interest rate of 7.25%And I’m going to give you $150 of cash flow per monthUse a 5% appreciation amount for your property per yearLet’s see what happens after 5 years:After 5 years…$150 of cash flow per month = $9,000Your mortgage has been paid down to $227,000 = $13,000Your property is now worth $382,000 = $82,000So that’s $9,000 of cash flow, $13,000 of principle buy down, and $82,000 of appreciation.