I feel like I only need to incorporate DSCRs, NPV, IRR and of course growth rates (both expense and rent). 

From a cash flow perspective, you’d really need to think long and hard about the cost of leveraging these properties, especially in the current rate market.Yes a bigger purchase price might mean a greater potential of higher gross cash flow and appreciation, but that cash flow might get eroded fairly quickly if these moderate interest rates are here to stay.- REI CPA from CA

However, if it needs that much work you are probably better off going with a hard money loan and then doing a rate & term refi once rehabbed.

Does it make sense to pay a premium for cheap interest rates with seller financing, or would it just be better to put 25% and forget about my 15% criteria and just go for distressed sellers and just get a commercial loan. 

On top of that, many companies are moving to using credit as a rating feature in their alga-rhythms.

To address this, we agreed that I would work in the business for six months to verify the financials, which so far align with his POS system.My main issue is that at 23, I don't have strong financials to get a conventional loan at 75% LTV with a ~7% rate, and the seller's lack of financials complicates bank approval.

At that time, the builder will pay the accumulated interest along with the principal.We have discussed a few different options to structure this arrangement, assuming an interest rate for interest-only loans with monthly payments is 10%:Option 1: delayed interest with a rate of 12% (interest rate is 2% higher)Option 2: charge a lower interest of 8% then profit share (need to determine appropriate % split)Any other thoughts on how to structure this arrangement?

After 4 months they give you the opportunity to open a secured credit cardAnother is called "Kikoff": These guys will report a $500 Limit Credit Line for less than 5 bucks a month.These modern services are a great place to start, they will never report late payments, won't get you into debt and build your credit score every bit as much as credit cards.After you 3 - 5 of these open for 90 days THEN apply for credit cards, you will get much better approvals, higher limits, lower rates, more rewards etc...Mortgage lenders will also be looking at how long those accounts have been open.

If I remember correctly, the redemption rate in CHS county is something like 80-90% and the interest that can be earned is capped.

First, I would raise the rent slightly higher than market rate and see if the smoker stays.