Going from 17% to 34% CoC ROI - Am I missing something?

[Pawan W.]

A rental property I bought last year and just getting refinanced. Here are the numbers for before and after. If I am to remove the vacacy and maintenance factor (considering the lease is for 2 years and I have a home warranty that the tenant pays deductible for - the ROI shoots up to 45%)

Initial Purchase	Post Refinance
Purchase Price	$ 105,000	Appraised For	$ 144,000
Paid at Settlement	$ 34,000	Cash Out	$ 26,060
Updates	$ 9,000
Total Cash Investment	$ 43,000	Post Refi Cash Investment	$ 16,940
Rent	$ 1,450	Rent	$ 1,450
PITI	$ 600	PITI	$ 741
HOA	$ 35	HOA	$ 35
Vacancy and Maintenance	$ 145	Vacancy and Maintenance	$ 145
Expenses	$ 780	Expenses	$ 921
Monthly Cash Flow	$ 670	Monthly Cash Flow	$ 529
Yearly CF	$ 8,040	Yearly CF	$ 6,350
Less Home Warranty	$ 529	Less Home Warranty	$ 529
NET Yearly Cash Flow	$ 7,511	NET Yearly Cash Flow	$ 5,821
CoC ROI	17%	CoC ROI	34%

Am I missing something here? Would you say this is an exception or typically achievable? With these kind of returns who needs to invest in stock market! (I understand diversification)