Various new landlord questions

[William Donaldson]

Greetings BP! I recently closed on my first investment property as a 20 year-old college student. I will save over $6k in rent/year while I finish my undergrad and will live for free while cash-flowing $200-300 a month after all expenses. I think it's a good first step, not a home-run, for my future investing career. With that in mind, I have a few questions:

---I will be furnishing the unit (4br/4ba) as it brings in $30 more per month per person. Where is the best place to find affordable, durable furniture? The furniture stores I've seen have more expensive, custom furniture and Craigslist is a decent option but will not provide all the furniture I need in a timely manner. I'd like for most of it (dressers/nightstands) to be identical.
---Where can I find the best information on what I can put in a SC lease? My father has investment properties and therefore a lease contract, but I want to make sure my lease has everything in it that I need and is legally allowed.
---How do I issue a cash receipt for when a tenant pays in cash?
---I had to obtain an investor-type loan (6.5%) because I had no credit (but had cash/past income). Will paying a mortgage boost my credit enough in a year to refinance at a lower rate (FHA)? Is there a way to estimate my future credit score?

I may post more questions in the thread. I appreciate any and all help you can provide! Thanks!