Paying a bit more might be justified if the pro forma income is very achievable, but $360,000 seems too high unless renovations are already complete.Factor in the costs and timeline for completing renovations for the studio and the fifth park-owned home.

I completely agree with @Ashish Acharya's points about the cost-effectiveness of a HELOC and the potential credit implications if it’s secured by your primary residence.

Perhaps if your partner was a general contractor or handyman type there may be some merit there to reduce costs / increase profitability.If your partner enjoys deal sourcing, a better move might be for him to become an agent - so he could legally collect commissions from finding deals and managing properties for multiple people. 

Here's a big "math" you overlooked for quite a few years.Right now $388k in equity, minus (let's go all out) $100k in closing costs, gets you a walk away of $288k in equity.Use that $288k as a 20% DP, and you should have $1.44M in property value,...not $415k. 

I don't expect to know everything by then, but I hope to develop a basic strategy that prevents me from making the most common and costly mistakes that a newbie can make.

If a prop is 250k and you can refi at 70% LTV you want to get it at 175k minus rehab costs.

I can't imagine flying out there for a day or two with a hotel can cost you $10K.Flying out there is like you paying for an insurance. 

A good landlord understands that vacancies & Rent-Ready costs will destroy your cashflow and profits.

I'm not satisfied with not filing the rental in an LLC simply because it's more simple and might cost me an additional filing fee .

You will incur more lending costs but you will only be in the first loan for 6 months.