I've come up with a strategy to target a market with potential for massive growth in the next few years, and purchase first-position tax liens on vacant lots properly zoned for multi-family.

In the last 10 years the population growth is moving to the south and to the west.

I am looking to put together a portfolio over the next 10 years that produces good income and allows me to pursue real estate or other business opportunities and leave the corporate world at the age of 45.My biggest concerns are regarding using debt to grow the business.

As you grow, the entity will be able to get Business lines of credit, business loans and other benefits that eventually you will be evele to do with out a personal guarantee.

Job growth?

Second I assume you are looking for single family houses for long term rentals to hold and not rehabs or commercial properties.If that's the case you need to be very careful investing from afar in single family houses as the dynamics are different.Do not be sold on a property where they say it's CLOSE to this great area etc.Instead look at population growth, quality of schools, the economic planning department, permits pulled for building, whether the state is business friendly and whether it is a pro-tenant or pro-landlord state, median income levels, job growth, and crime levels ( violent versus non-violent offenses ) etc.Many more metrics to look at but this will get you started.

Been following growth and demographic patterns and these seem like great areas to invest in.

Is there potential for rent growth?

The Bigger Pockets community has been instrumental in my investing growth!