Have Actual Budget track a home's zestimate. Add "zestimate:https://www.zillow.com/homedetails/HOME/ID_zpid/" to the account note. If you own a percent of the house, add "ownership:0.50" to the note. Run `npm install` to install packages, then `node zestimate.js` to run it (I run it in a weekly/monthly cron).

package.json

{
  "dependencies": {
    "@actual-app/api": "^6.8.1",
    "dotenv": "^16.4.5",
    "jsdom": "^24.1.0"
  }
}

zestimate.js

require("dotenv").config();

const api = require('@actual-app/api');

const payeeName = process.env.IMPORTER_PAYEE_NAME || 'Zestimate';
const url = process.env.ACTUAL_SERVER_URL || '';
const password = process.env.ACTUAL_SERVER_PASSWORD || '';
const file_password = process.env.ACTUAL_FILE_PASSWORD || '';
const sync_id = process.env.ACTUAL_SYNC_ID || '';
const cache = process.env.IMPORTER_CACHE_DIR || './cache';

if (!url || !password || !sync_id) {
  console.error('Required settings for Actual not provided.');
  process.exit(1);
}

const jsdom = require("jsdom");

async function getZestimate(URL) {
  const response = await fetch(URL, {
    headers: {
      'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36',
      'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8',
      'Accept-Language': 'en-GB,en;q=0.6',
      'Referer': 'https://www.google.com/',
    }
  });

  const html = await response.text();
  const dom = new jsdom.JSDOM(html);

  const zestimateText = dom.window.document.getElementById('home-details-home-values').getElementsByTagName('h3')[0].textContent;
  return parseInt(zestimateText.replace('$', '').replace(',', '')) * 100;
}

function sleep(ms) {
  return new Promise((resolve) => {
    setTimeout(resolve, ms);
  });
}

const getAccountBalance = async (account) => {
  const data = await api.runQuery(
    api.q('transactions')
      .filter({
        'account': account.id,
      })
      .calculate({ $sum: '$amount' })
      .options({ splits: 'grouped' })
  );
  return data.data;
};

(async function() {
  console.log("connect");
  await api.init({ serverURL: url, password: password, dataDir: cache });

  console.log("open file");
  if (file_password) {
    await api.downloadBudget(sync_id, { password: file_password, });
  } else {  
    await api.downloadBudget(sync_id);
  }

  const payees = await api.getPayees();
  let payeeId = payees.find(p => p.name === payeeName).id;
  if (!payeeId) {
    payeeId = await api.createPayee({ name: payeeName });
  }
  if (!payeeId) {
    console.error('Failed to create payee:', payeeName);
    process.exit(1);
  }

  const accounts = await api.getAccounts();
  for (const account of accounts) {
    const notes = await api.runQuery(
      api.q('notes')
        .filter({
          id: `account-${account.id}`,
        })
        .select('*')
      );

      if (notes.data.length && notes.data[0].note) {
        const note = notes.data[0].note;

        if (note.indexOf('zestimate:') > -1) {
          const URL = note.split('zestimate:')[1].split(' ')[0];

          let ownership = 1;
          if (note.indexOf('ownership:') > -1) {
            ownership = parseFloat(note.split('ownership:')[1].split(' ')[0]);
          }

          console.log('Fetching zestimate for account:', account.name);
          console.log('Zillow URL:', URL);

          const zestimate = await getZestimate(URL);
          const balance = await getAccountBalance(account);
          const diff = (zestimate * ownership) - balance;

          console.log('Zestimate:', zestimate);
          console.log('Ownership:', zestimate * ownership);
          console.log('Balance:', balance);
          console.log('Difference:', diff);

          if (diff != 0) {
            await api.importTransactions(account.id, [{
              date: new Date(),
              payee: payeeId,
              amount: diff,
              notes: `Update Zestimate to ${zestimate * ownership / 100} (${zestimate / 100}*${ownership * 100}%)`,
            }]);
          }

          await sleep(1324);
        }
      }  
  }

  console.log("done");
  await api.shutdown();
})();