Hello Lib213,
Congratulations on starting your real estate part-time self-employment activity.
Best suggestion, I can provide, is to keep good records for the expenses related to this activity. This way you will not feel that you are shorting yourself.
To be deductible, a business expense must be both ordinary and necessary. Here is an IRS Publication 535, Business Expenses, for more details. Here is another IRS article, how businesses can deduct startup costs.
Hope it helps.