I would just take into account that a lower down payment will mean a higher monthly payment so be sure to run the numbers conservatively in order to ensure your STR revenue is able to carry your monthly payment with this higher mortgage cost. 

If I have lump-sum free cash, should I just apply it to my mortgage to recast so that my monthly goes lower?

Seems like it's in a lower end area so if it is filled you will have tenant issues and turnover cost.

Which is why I pay more, for less cash flow in highly desirable areas.In high income areas, rent is a lower proportion of income so therefore your tenants have a higher capacity for paying higher rent because rent is less than 20% or even 10% of their income.

You’re able to learn the basics of a real estate investment with lower risk and build equity at the same time.Because you're in the military, you'll be able to enter a property with 0% down which means you can leverage your money way more effectively. 

that we’ve learned in our 24 years, managing almost 700 doors across the Metro Detroit area, including almost 100 S8 leases:Class A Properties:Cashflow vs Appreciation: Typically, 3-5 years for positive cashflow, but you get highest relative rent & value appreciation.Vacancy Est: Historically 10%, 5% the more recent norm.Tenant Pool: Majority will have FICO scores of 680+ (roughly 5% probability of default), zero evictions in last 7 years.Class B Properties:Cashflow vs Appreciation: Typically, decent amount of relative rent & value appreciation.Vacancy Est: Historically 10%, 5% should be applied only if proper research done to support.Tenant Pool: Majority will have FICO scores of 620-680 (around 10% probability of default), some blemishes, but should have no evictions in last 5 yearsClass C Properties:Cashflow vs Appreciation: Typically, high cashflow and at the lower end of relative rent & value appreciation.

@Damon AlbersSounds like these properties are in a class c area and your manager is not doing a good job vetting themBut this is not out of ordinary for c class rentals which is why people look at cash flow and be like wow but one $5000 bill can wipe out 4-6 months of rental income and properties never make money and rarely appreciateThis is why we do not do lower class rentals as stated cash flow vs reality are typically not close

PROS of a Solo 401(k) with no Custodian: 1) Freedom of checkbook control, ability to more easily move funds in and out of a bank account in the name of the Solo 401(k). 2) In some cases, lower fees. 3) Ability to more easily link your Solo 401(k) to bank account systems like rental property management systems, or if investing in real estate syndication platforms. 

I'm going to start reaching out soon to a friend of a family member who owns a local PM group with roughly 1000 doors for lower income, just to pick his brain, but I can envision a scenario where if I needed to partner with someone to get my first deal and gain some creditability and experience, he may be willing to assist.

That's most likely going to be a C- neighborhood or lower so there could be more perceived scale to BRRRR, but a tougher decision on how to renovate at that price point and possibly harder tenancies.I would get to real estate investor meetups in your area.