E-Signature API for Real Estate: Automate Lease Agreements, Purchase Contracts, and Closings

[Tenant Screening Platform]
       │
       ▼ (1) Background & Credit Check Passes
[Database Record: status="APPROVED"]
       │
       ▼ (2) Compile Residential Lease Template (Markdown)
[Signbee REST API: POST /api/v1/send]
       │
       ├──> (3) Renders PDF with unit details, rent, rules, pet addendum
       │
       ▼ (4) Automated Email Dispatched to Tenant
[Tenant Reviews & Signs in Mobile Browser]
       │
       ▼ (5) POST /api/webhooks/signbee (event: document.signed)
[Property Management Backend]
       │
       ├──> (6) Charge 1st Month Rent & Security Deposit via Stripe
       ├──> (7) Provision Smart Lock Digital Keycode via Seam API
       └──> (8) Store Signed PDF + SHA-256 Audit Certificate in S3

interface LeaseData {
  tenantName: string;
  tenantEmail: string;
  propertyAddress: string;
  unitNumber: string;
  monthlyRent: number;
  securityDeposit: number;
  commencementDate: string;
  expirationDate: string;
  petAddendum: boolean;
}

export async function dispatchResidentialLease(data: LeaseData) {
  const markdownLease = `# Residential Lease Agreement

**Property:** ${data.propertyAddress}, Unit ${data.unitNumber}
**Commencement Date:** ${data.commencementDate}
**Expiration Date:** ${data.expirationDate}

## 1. Parties
- **Landlord:** BlueSky Properties Management LLC ("Landlord")
- **Tenant:** ${data.tenantName} ("Tenant")

## 2. Monthly Rent & Security Deposit
Tenant agrees to pay a monthly rent of **$${data.monthlyRent.toLocaleString()} USD** due on the first day of each calendar month.
Landlord acknowledges receipt of a security deposit equal to **$${data.securityDeposit.toLocaleString()} USD**.

## 3. Rules & Covenants
1. **Occupancy:** The premises shall be occupied strictly as a private residential dwelling.
2. **Maintenance:** Tenant shall maintain the property in a clean and sanitary condition.
${data.petAddendum ? "3. **Pet Addendum:** One domestic pet under 35 lbs permitted. Additional $50/mo pet rent applies." : "3. **Pets:** No pets permitted on premises without written approval."}

By signing below, the parties agree to all lease covenants.`;

  const response = await fetch("https://signb.ee/api/v1/send", {
    method: "POST",
    headers: {
      "Authorization": `Bearer ${process.env.SIGNBEE_API_KEY}`,
      "Content-Type": "application/json",
    },
    body: JSON.stringify({
      markdown: markdownLease,
      sender_name: "BlueSky Property Management",
      sender_email: "leasing@bluesky-props.io",
      recipient_name: data.tenantName,
      recipient_email: data.tenantEmail,
      webhook_url: "https://api.bluesky-props.io/v1/webhooks/signbee",
      expires_in_days: 5,
    }),
  });

  if (!response.ok) {
    const errorText = await response.text();
    throw new Error(`Failed to dispatch lease agreement: ${errorText}`);
  }

  const result = await response.json();
  return {
    documentId: result.document_id,
    signingUrl: result.signing_url,
  };
}