So on numerous occasions, I have expressed my concerns about staying within my budget.Now on top of this, the property manager let the pipes freeze and they leaked and the boiler also cracked which I was told to file an insurance claim.

Also you seem to be motivated to build since you already have these lots. 

You would be surprised how much Wayfair marks stuff up, and that a lot of things that are marketed as unique are sold by numerous retailers. 

Since most people who are not actively seeking a sale are not motivated to sell at anything other than a top of the line price, this is going to be a numbers game of x thousands of contacts for every potentially doable deal.  

It’s very motivating to hear how you did it!

Unfortunately looking like this specific deal likely won't pan out; seller is definitely not motivated to offload quickly/discounted based on their replies.I found a realtor through BP who I'm now working with to find a property, so progress in the right direction!

Sounds like you have the motivation & ambitious but precise goals.

Sometimes it's ambiguous, but even then, why should I bother with the company that has numerous unresolved lawsuits, versus another company that is virtually the same but has none.

Understanding their motivations allows you to frame your offer in a way that aligns with their goals.

Search the BP for ADU appraisals to encounter numerous examples.