The full contribution to the Roth IRA is available to grow tax free without any reduction for taxes that have already been paid.So, in your example, it is not true that the Roth only has $65K to start with after $100K in contributions have been made.

One of my market rate units has asked for a -15% monthly reduction.

The disadvantage is that nonresident state filings are a PITA and result in higher CPA fees.Some states require nonresident withholding on state tax on a gain which in theory might satisfy all the tax (perhaps even overpay a bit).The technically correct answer is that you might still be required to file, but the practical answer is that it might not be worth the administrative costs.Ultimately the decision probably comes down to a cost benefit analysis to see if the filing burden and cost justifies the reduction in tax you might owe.

Just another quick question, Because I was unaware of the situation before going under contract, do you think now knowing this a $10-15k reduction wouldn’t be out of the question of asking?  

If it takes you multiple years to save up money to invest those are valuable years lost of cash flow, tax benefits/depreciation, appreciation & debt reduction by the tenant paying the loan down.

Buy all 8 of those properties as fast as you can and then focus on debt reduction after that. 

(See note above about earlier extra payments being worth more when trying to figure out why which payments go to which same rate loans saves you more or less money.)On the Contrary, Infinite banking is a concept using permanent life insurance the concept mentioned in this post is about velocity banking, mortgage debt acceleration, and a few other names that involves taking idle funds that would typically be parked in a checking/savings and using it to accelerate debt payoff and interest reduction.

When a payment is received half of the amortized principal goes to your principal reduction or your cash paid out as the return to capital, the rest is profit and it is treated as interest on your investment.

In some seller's market, this is harder to do and might be less. however, in a buyer's market i would start with a 15% reduction...after a counteroffer, you know that the seller is willing to talk more on price rather than just rejecting your offer period.

There's no point in agreeing to $100 reduction and then finding out you don't even meet my qualification standards.Show them you're worth the effort first, then negotiate.