Quote from @John Davey: Id appreciate any help, as ex. if i take out say 100k home equity loan and use 50k each as down payments/cloing costs my understanding is i cant deduct the interest?

Properties typically on a land lease in communities like this are more difficult to get financing on - so not only check the values but also time it takes for these properties to sell to understand your holding costs

The Highway 64 property presented a great opportunity due to its low acquisition cost and potential for substantial value increase.

Is just the fact that no garage could be a no go for some buyers enough to build it even if it only raises the value by the actual cost?

Maybe 1500 other closing costs, so 6k total. 

It was in rough condition, which limited competition and made it a strong candidate for the BRRRR method.Negotiation: After analyzing comps and repair costs, I negotiated a $420,000 purchase price, which was below the market value for similar properties in the area.

Cost overruns were tremendous.

Typically starting with a smaller rehab budget of $50K or less (maybe a max of $75K) and avoiding a 1 to 1(or higher) ratio of purchase to rehab costs is recommend when you are first starting out. 

Understand the fees involved and calculate the total cost for an entire year of management so you can compare the different managers.

Credit cards have the same limitation on the amount you can borrow and will likely end up costing more than private lenders.