Submitting an offer for a multi-family apartment building typically involves several steps:

1. Conduct thorough research: Gather information about the property, market conditions, and recent comparable sales to determine a competitive and fair offer price.

2. Get pre-approved for financing: Obtain a pre-approval letter from a lender to show the seller that you are a serious and qualified buyer.

3. Engage with the seller or their agent: Express your interest in submitting an offer and request any necessary documentation about the property.

4. Prepare the offer: Draft a written offer that includes the purchase price, contingencies (such as inspections and financing), earnest money deposit, and proposed closing date.

5. Submit the offer: Present the offer to the seller or their agent, either in person, via email, or through a real estate platform.

6. Be responsive and open to negotiations: Be prepared for counteroffers and negotiate the terms until both parties reach an agreement.

7. Due diligence: Once the offer is accepted, conduct thorough inspections and review any documents related to the property.

It is helpful to work with a knowledgeable real estate agent or attorney who can guide you through the process and ensure that your offer is competitive and legally sound.