It seems like I'm always a day late to most parties and just don't want to jump into a new career/venture only to find in the next 10 years, all my investments are diluted due to the increase in inventory. 

Anything that you cannot prove was caused by tenant, let it go. if they take you to court you will most likely lose. any rehab costs should have been considered in your acquisition price.

You could lose your buyer by allowing the tenants to leave.

I was kind of wanting to start smaller for my first property, and keep to around 40-50k (that way if it didn't work out, I could afford to pay the loan and not lose my house).I'll also be transferring the cash to an LLC in order to build equity/assests for that, so that's a reason I decided to go the route I'm going.

Vacation rental may not be the best investment for your 401k, and because you can't manage it yourself should you live your money in the mercy of the stock market or in the money market account losing it's purchasing power to inflation?

I just feel like they may be losing out on a lot of business due to the 80% rule.

For flipping no it is not, because lets assume purchase price 470k + 27k in repairs = $497k it will probably cost at least 5% of the sale price in realtor fees and closing costs probably more so ($525k x 5%)= $26,250So $497k + 26k = $523k thus in a best case scenario you risk half a million dollars to make $2,000 if anything goes wrong you lose money, if you have to borrow you probably lose money.

Tracking investment opportunities and not losing site of them overtime... 

•The investment could be structured in many ways: secured or unsecured promissory note, joint venture, etc.

(Note: in an option contract, the amount you pay the seller as 'valuable consideration' will be his to keep regardless of whether or not you exercise or assign the option to someone else... so be sure that you can afford to lose this money if you cannot find a buyer prior to the option expiring.)3.