@Dustin Espinoza, hi and welcome to BP!
Yes, you have gotten a good start by asking to find out what you don't know. There are a lot of things you need to know to analyze a property. I'll try to cover some basics, but there is much more to be said:
1) Expenses (taxes, insurance, maintenance, property management, utilities, lawn care, snow removal, legal fees).
2) Vacancy rate.
3) Capital Expense reserves. How much you will set aside each month to cover big ticket items like HVAC systems, roofs, and kitchen / bath upgrades.
4) Profit expectation.
5) Debt service, if you plan to borrow some or all of the purchase and fix up costs.
A few rules of thumb:
1) A smaller property (under 50 units) that doesn't meet the 1% rarely cash flows positively. To calculate the rule, take the MONTHLY gross potential rent (market rent for all units at 100% rented) and divide by the total "all in" costs to bring the units online: purchase price, rehab, closing costs, holding costs. For example, let's say your property costs $75,000 per unit and you will spend $5,000 on average per unit in fix up costs. Closing costs for the property are $5,000 and you have to hold it vacant for 2 months, during which time you spend $800 on lawn care and utilities. Add up all your costs ($75,000 x 10 units + $5,000 X 10 units + $5,000 + $800) gives you an "all in" cost of $805,800. The combined monthly rents must be AT LEAST $8,085 or about $800 per unit per month. $8,085 / $805,800 = 1%.
2) Always include all expenses, even if you plan to DIY. For example, property management and maintenance are two areas many "investors" buy themselves a volunteer job: they do they work to "save" money, but they work for free. Pay yourself, even if that means simply take that amount of money and put it into a savings account or use it to pay down extra debt. Any other investor will value the deal assuming there is hired out maintenance and property management, so you should include those costs too to get a true Return on Investment.
3) Smaller properties (<50 units) are usually not self-sustaining enough to hire a full time PM and maintenance man, so they will not be attractive to larger investors. This is important to consider for your exit strategy. Whom are you selling to, assuming you plan on selling?
4) What are your goal(s)? Monthly cash flow, appreciation, both?
That's a lot to think about for now. You can probably get most of the info on expenses from the Seller's Schedule E income tax filing, assuming the property is owned by an individual. I would make that a condition of any offer. Ask for their expenses up front, but then make the offer contingent on verifying expenses on official tax records. Sellers tend to "forget" (lie) about expenses except when it comes to tax time, because that's when reporting all of your expenses saves on taxes.
I hope this is helpful.