The answer to your question will be found in your lease agreement and no one here has read it so any advice would not add tremendous value.

Sale-Leasebacks have inherent challenges because the tenant/seller is incentivized to market the property in such a way they get they price they want, but if the entity who signs the lease is weak and there's no personal guarantor, they could stop paying rent the day after you close leaving you high and dry with very little legal remedy.I don't know your market, but in my eyes, any 10% cap offering is either an extremely weak tenant OR a tenant that has very little term remaining with no plans to renew.If I were, you I would very seriously consider how much I like the real estate and what my odds would be of refilling the real estate with the same or better rent and/or a better credit tenant once this tenant goes belly up.

As building this house and accumulating land has been something I have always want to be able to pass down in my family, I am worried that to pursue this plan, I will be left with no more real estate assets after this goal is accomplished.

Also, I have about $8k in cash and no debt at all! 

The best thing to do is call a few local lenders in your area and explain what you are looking to do and ask what options are available for that scenario. 

If it is, it will be a no go for most DSCR lenders, however can be done on a commercial, no doc loan at a high rate. 

All the ones I've called will get a percentage of what they collect and don't charge anything more.

No way I would refinance off at 3.5% loan...... not going to get anywhere close to that... do a HELOC or another LOC.

We track most things manually, but use Apartments.com for the units currently occupied (adding more units in our portfolio will incur the Apartments.com premium cost, so I want to explore my options if software is no longer free). 

Call some local hard money lenders and ask who they use.